diff --git a/README.md b/README.md
index 882fef7..48afb79 100644
--- a/README.md
+++ b/README.md
@@ -19,12 +19,12 @@ For purposes of the BOSL2 library, the following terms apply:
 
 ## Common Arguments:
 
-Args    | What it is
-------- | ----------------------------------------
-fillet  | Radius of rounding for interior or exterior edges.
-chamfer | Size of chamfers/bevels for interior or exterior edges.
-orient  | Axis a part should be oriented along.  Given as an XYZ triplet of rotation angles.  It is recommended that you use the `ORIENT_` constants from `constants.scad`.  Default is usually `ORIENT_Z` for vertical orientation.
-anchor  | Side of the object that should be anchored to the origin. Given as a vector towards the side of the part to align with the origin.  It is recommended that you use the directional constants from `constants.scad`.  Default is usually `CENTER` for centered.
+Args     | What it is
+-------- | ----------------------------------------
+rounding | Radius of rounding for interior or exterior edges.
+chamfer  | Size of chamfers/bevels for interior or exterior edges.
+orient   | Axis a part should be oriented along.  Given as an XYZ triplet of rotation angles.  It is recommended that you use the `ORIENT_` constants from `constants.scad`.  Default is usually `ORIENT_Z` for vertical orientation.
+anchor   | Side of the object that should be anchored to the origin. Given as a vector towards the side of the part to align with the origin.  It is recommended that you use the directional constants from `constants.scad`.  Default is usually `CENTER` for centered.
 
 
 ## Examples
@@ -85,6 +85,7 @@ The library files are as follows:
   - [`vectors.scad`](https://github.com/revarbat/BOSL2/wiki/vectors.scad): Vector math functions.
   - [`matrices.scad`](https://github.com/revarbat/BOSL2/wiki/matrices.scad): Matrix math and affine transformation functions.
   - [`coords.scad`](https://github.com/revarbat/BOSL2/wiki/coords.scad): Coordinate system conversions and point transformations.
+  - [`geometry.scad`](https://github.com/revarbat/BOSL2/wiki/geometry.scad): Functions to calculate various geometry.
   - [`quaternions.scad`](https://github.com/revarbat/BOSL2/wiki/quaternions.scad): Functions to work with quaternion rotations.
   - [`convex_hull.scad`](https://github.com/revarbat/BOSL2/wiki/convex_hull.scad): Functions to generate 2D and 3D hulls of points.
   - [`triangulation.scad`](https://github.com/revarbat/BOSL2/wiki/triangulation.scad): Functions to triangulate `polyhedron()` faces.
diff --git a/attachments.scad b/attachments.scad
index 5af3881..1911d1b 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -106,6 +106,7 @@ function find_anchor(anchor, h, size, size2=undef, shift=[0,0], extra_anchors=[]
 				two_d? sidevec :
 				anchor==CENTER? UP :
 				norm([anchor.x,anchor.y]) < EPSILON? anchor :
+				norm(size)+norm(size2) < EPSILON? anchor :
 				abs(anchor.z) < EPSILON? sidevec :
 				anchor.z>0? (UP+sidevec)/2 :
 				(DOWN+sidevec)/2
@@ -162,6 +163,7 @@ function _str_char_split(s,delim,n=0,acc=[],word="") =
 //   `$parent_orient` is set to the parent object's `orient` value.
 //   `$parent_anchor` is set to the parent object's `anchor` value.
 //   `$parent_anchors` is set to the parent object's list of non-standard extra anchors.
+//   `$parent_2d` is set to the parent object's `two_d` value.
 //
 // Example:
 //   #cylinder(d=5, h=10);
@@ -248,14 +250,14 @@ module orient_and_anchor(
 //   Attaches children to a parent object at an anchor point and orientation.
 // Arguments:
 //   name = The name of the parent anchor point to attach to.
-//   to = The name of the child anchor point.
-//   overlap = Amount to sink child into the parent.
-//   norot = If true, don't rotate children when attaching to the anchor point.
+//   to = Optional name of the child anchor point.  If given, orients the child such that the named anchors align together rotationally.
+//   overlap = Amount to sink child into the parent.  Equivalent to `down(X)` after the attach.
+//   norot = If true, don't rotate children when attaching to the anchor point.  Only translate to the anchor point.
 // Example:
 //   spheroid(d=20) {
-//       attach(TOP)   down(1.5) cyl(l=11.5, d1=10, d2=5, anchor=BOTTOM);
+//       attach(TOP) down(1.5) cyl(l=11.5, d1=10, d2=5, anchor=BOTTOM);
 //       attach(RIGHT, BOTTOM) down(1.5) cyl(l=11.5, d1=10, d2=5);
-//       attach(FRONT) down(1.5) cyl(l=11.5, d1=10, d2=5, anchor=BOTTOM);
+//       attach(FRONT, BOTTOM, overlap=1.5) cyl(l=11.5, d1=10, d2=5);
 //   }
 module attach(name, to=undef, overlap=undef, norot=false)
 {
@@ -296,6 +298,8 @@ module tags(tags)
 //   recolor(c) ...
 // Description:
 //   Sets the color for children that can use the $color special variable.
+// Arguments:
+//   c = Color name or RGBA vector.
 // Example:
 //   recolor("red") cyl(l=20, d=10);
 module recolor(c)
@@ -308,7 +312,13 @@ module recolor(c)
 // Module: hide()
 // Usage:
 //   hide(tags) ...
-// Description: Hides all children with the given tags.
+// Description:
+//   Hides all children with the given tags.
+// Example:
+//   hide("A") cube(50, anchor=CENTER, $tags="Main") {
+//       attach(LEFT, BOTTOM) cylinder(d=30, l=30, $tags="A");
+//       attach(RIGHT, BOTTOM) cylinder(d=30, l=30, $tags="B");
+//   }
 module hide(tags="")
 {
 	$tags_hidden = tags==""? [] : _str_char_split(tags, " ");
@@ -319,7 +329,13 @@ module hide(tags="")
 // Module: show()
 // Usage:
 //   show(tags) ...
-// Description: Shows only children with the given tags.
+// Description:
+//   Shows only children with the given tags.
+// Example:
+//   show("A B") cube(50, anchor=CENTER, $tags="Main") {
+//       attach(LEFT, BOTTOM) cylinder(d=30, l=30, $tags="A");
+//       attach(RIGHT, BOTTOM) cylinder(d=30, l=30, $tags="B");
+//   }
 module show(tags="")
 {
 	$tags_shown = tags==""? [] : _str_char_split(tags, " ");
@@ -343,6 +359,12 @@ module show(tags="")
 //   neg = String containing space delimited set of tag names of children to difference away.
 //   pos = String containing space delimited set of tag names of children to be differenced away from.
 //   keep = String containing space delimited set of tag names of children to keep whole.
+// Example:
+//   diff("neg", "pos", keep="axle")
+//   sphere(d=100, $tags="pos") {
+//       attach(CENTER) xcyl(d=40, h=120, $tags="axle");
+//       attach(CENTER) cube([40,120,100], anchor=CENTER, $tags="neg");
+//   }
 module diff(neg, pos=undef, keep=undef)
 {
 	difference() {
@@ -382,6 +404,12 @@ module diff(neg, pos=undef, keep=undef)
 //   a = String containing space delimited set of tag names of children.
 //   b = String containing space delimited set of tag names of children.
 //   keep = String containing space delimited set of tag names of children to keep whole.
+// Example:
+//   intersect("wheel", "mask", keep="axle")
+//   sphere(d=100, $tags="wheel") {
+//       attach(CENTER) cube([40,100,100], anchor=CENTER, $tags="mask");
+//       attach(CENTER) xcyl(d=40, h=100, $tags="axle");
+//   }
 module intersect(a, b=undef, keep=undef)
 {
 	intersection() {
diff --git a/examples/attachments.scad b/examples/attachments.scad
index 8a3c1f3..f208b20 100644
--- a/examples/attachments.scad
+++ b/examples/attachments.scad
@@ -2,7 +2,7 @@ include <BOSL2/std.scad>
 
 $fn=32;
 
-cuboid([60,40,40], fillet=5, edges=EDGES_Z_ALL, anchor=BOTTOM) {
+cuboid([60,40,40], rounding=5, edges=EDGES_Z_ALL, anchor=BOTTOM) {
 	attach(TOP, BOTTOM) rounded_prismoid([60,40],[20,20], h=50, r1=5, r2=10) {
 		attach(TOP) cylinder(d=20, h=30) {
 			attach(TOP) cylinder(d1=50, d2=30, h=12);
diff --git a/shapes.scad b/shapes.scad
index 4233f7e..67521c7 100644
--- a/shapes.scad
+++ b/shapes.scad
@@ -1108,520 +1108,6 @@ module onion(cap_h=undef, r=undef, d=undef, maxang=45, h=undef, orient=ORIENT_Z,
 }
 
 
-// Module: narrowing_strut()
-//
-// Description:
-//   Makes a rectangular strut with the top side narrowing in a triangle.
-//   The shape created may be likened to an extruded home plate from baseball.
-//   This is useful for constructing parts that minimize the need to support
-//   overhangs.
-//
-// Usage:
-//   narrowing_strut(w, l, wall, [ang], [orient], [anchor]);
-//
-// Arguments:
-//   w = Width (thickness) of the strut.
-//   l = Length of the strut.
-//   wall = height of rectangular portion of the strut.
-//   ang = angle that the trianglar side will converge at.
-//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `FRONT`.
-//
-// Example:
-//   narrowing_strut(w=10, l=100, wall=5, ang=30);
-module narrowing_strut(w=10, l=100, wall=5, ang=30, orient=ORIENT_Y, anchor=FRONT)
-{
-	h = wall + w/2/tan(ang);
-	size = [w, h, l];
-	orient_and_anchor(size, orient, anchor, chain=true) {
-		fwd(h/2) {
-			linear_extrude(height=l, center=true, slices=2) {
-				back(wall/2) square([w, wall], center=true);
-				back(wall-0.001) {
-					yscale(1/tan(ang)) {
-						difference() {
-							zrot(45) square(w/sqrt(2), center=true);
-							fwd(w/2) square(w, center=true);
-						}
-					}
-				}
-			}
-		}
-		children();
-	}
-}
-
-
-// Module: thinning_wall()
-//
-// Description:
-//   Makes a rectangular wall which thins to a smaller width in the center,
-//   with angled supports to prevent critical overhangs.
-//
-// Usage:
-//   thinning_wall(h, l, thick, [ang], [strut], [wall], [orient], [anchor]);
-//
-// Arguments:
-//   h = height of wall.
-//   l = length of wall.  If given as a vector of two numbers, specifies bottom and top lengths, respectively.
-//   thick = thickness of wall.
-//   ang = maximum overhang angle of diagonal brace.
-//   strut = the width of the diagonal brace.
-//   wall = the thickness of the thinned portion of the wall.
-//   orient = Orientation of the length axis of the wall.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_X`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
-//
-// Example: Typical Shape
-//   thinning_wall(h=50, l=80, thick=4);
-// Example: Trapezoidal
-//   thinning_wall(h=50, l=[80,50], thick=4);
-module thinning_wall(h=50, l=100, thick=5, ang=30, strut=5, wall=2, orient=ORIENT_Z, anchor=CENTER)
-{
-	l1 = (l[0] == undef)? l : l[0];
-	l2 = (l[1] == undef)? l : l[1];
-
-	trap_ang = atan2((l2-l1)/2, h);
-	corr1 = 1 + sin(trap_ang);
-	corr2 = 1 - sin(trap_ang);
-
-	z1 = h/2;
-	z2 = max(0.1, z1 - strut);
-	z3 = max(0.05, z2 - (thick-wall)/2*sin(90-ang)/sin(ang));
-
-	x1 = l2/2;
-	x2 = max(0.1, x1 - strut*corr1);
-	x3 = max(0.05, x2 - (thick-wall)/2*sin(90-ang)/sin(ang)*corr1);
-	x4 = l1/2;
-	x5 = max(0.1, x4 - strut*corr2);
-	x6 = max(0.05, x5 - (thick-wall)/2*sin(90-ang)/sin(ang)*corr2);
-
-	y1 = thick/2;
-	y2 = y1 - min(z2-z3, x2-x3) * sin(ang);
-
-	size = [l1, thick, h];
-	orient_and_anchor(size, orient, anchor, size2=[l2,thick], chain=true) {
-		polyhedron(
-			points=[
-				[-x4, -y1, -z1],
-				[ x4, -y1, -z1],
-				[ x1, -y1,  z1],
-				[-x1, -y1,  z1],
-
-				[-x5, -y1, -z2],
-				[ x5, -y1, -z2],
-				[ x2, -y1,  z2],
-				[-x2, -y1,  z2],
-
-				[-x6, -y2, -z3],
-				[ x6, -y2, -z3],
-				[ x3, -y2,  z3],
-				[-x3, -y2,  z3],
-
-				[-x4,  y1, -z1],
-				[ x4,  y1, -z1],
-				[ x1,  y1,  z1],
-				[-x1,  y1,  z1],
-
-				[-x5,  y1, -z2],
-				[ x5,  y1, -z2],
-				[ x2,  y1,  z2],
-				[-x2,  y1,  z2],
-
-				[-x6,  y2, -z3],
-				[ x6,  y2, -z3],
-				[ x3,  y2,  z3],
-				[-x3,  y2,  z3],
-			],
-			faces=[
-				[ 4,  5,  1],
-				[ 5,  6,  2],
-				[ 6,  7,  3],
-				[ 7,  4,  0],
-
-				[ 4,  1,  0],
-				[ 5,  2,  1],
-				[ 6,  3,  2],
-				[ 7,  0,  3],
-
-				[ 8,  9,  5],
-				[ 9, 10,  6],
-				[10, 11,  7],
-				[11,  8,  4],
-
-				[ 8,  5,  4],
-				[ 9,  6,  5],
-				[10,  7,  6],
-				[11,  4,  7],
-
-				[11, 10,  9],
-				[20, 21, 22],
-
-				[11,  9,  8],
-				[20, 22, 23],
-
-				[16, 17, 21],
-				[17, 18, 22],
-				[18, 19, 23],
-				[19, 16, 20],
-
-				[16, 21, 20],
-				[17, 22, 21],
-				[18, 23, 22],
-				[19, 20, 23],
-
-				[12, 13, 17],
-				[13, 14, 18],
-				[14, 15, 19],
-				[15, 12, 16],
-
-				[12, 17, 16],
-				[13, 18, 17],
-				[14, 19, 18],
-				[15, 16, 19],
-
-				[ 0,  1, 13],
-				[ 1,  2, 14],
-				[ 2,  3, 15],
-				[ 3,  0, 12],
-
-				[ 0, 13, 12],
-				[ 1, 14, 13],
-				[ 2, 15, 14],
-				[ 3, 12, 15],
-			],
-			convexity=6
-		);
-		children();
-	}
-}
-
-
-// Module: braced_thinning_wall()
-//
-// Description:
-//   Makes a rectangular wall with cross-bracing, which thins to a smaller width in the center,
-//   with angled supports to prevent critical overhangs.
-//
-// Usage:
-//   braced_thinning_wall(h, l, thick, [ang], [strut], [wall], [orient], [anchor]);
-//
-// Arguments:
-//   h = height of wall.
-//   l = length of wall.
-//   thick = thickness of wall.
-//   ang = maximum overhang angle of diagonal brace.
-//   strut = the width of the diagonal brace.
-//   wall = the thickness of the thinned portion of the wall.
-//   orient = Orientation of the length axis of the wall.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
-//
-// Example: Typical Shape
-//   braced_thinning_wall(h=50, l=100, thick=5);
-module braced_thinning_wall(h=50, l=100, thick=5, ang=30, strut=5, wall=2, orient=ORIENT_Y, anchor=CENTER)
-{
-	dang = atan((h-2*strut)/(l-2*strut));
-	dlen = (h-2*strut)/sin(dang);
-	size = [l, thick, h];
-	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
-		union() {
-			xrot_copies([0, 180]) {
-				down(h/2) narrowing_strut(w=thick, l=l, wall=strut, ang=ang);
-				fwd(l/2) xrot(-90) narrowing_strut(w=thick, l=h-0.1, wall=strut, ang=ang);
-				intersection() {
-					cube(size=[thick, l, h], center=true);
-					xrot_copies([-dang,dang]) {
-						zspread(strut/2) {
-							scale([1,1,1.5]) yrot(45) {
-								cube(size=[thick/sqrt(2), dlen, thick/sqrt(2)], center=true);
-							}
-						}
-						cube(size=[thick, dlen, strut/2], center=true);
-					}
-				}
-			}
-			cube(size=[wall, l-0.1, h-0.1], center=true);
-		}
-		children();
-	}
-}
-
-
-
-// Module: thinning_triangle()
-//
-// Description:
-//   Makes a triangular wall with thick edges, which thins to a smaller width in
-//   the center, with angled supports to prevent critical overhangs.
-//
-// Usage:
-//   thinning_triangle(h, l, thick, [ang], [strut], [wall], [diagonly], [orient], [anchor|center]);
-//
-// Arguments:
-//   h = height of wall.
-//   l = length of wall.
-//   thick = thickness of wall.
-//   ang = maximum overhang angle of diagonal brace.
-//   strut = the width of the diagonal brace.
-//   wall = the thickness of the thinned portion of the wall.
-//   diagonly = boolean, which denotes only the diagonal side (hypotenuse) should be thick.
-//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
-//   center = If true, centers shape.  If false, overrides `anchor` with `UP+BACK`.
-//
-// Example: Centered
-//   thinning_triangle(h=50, l=80, thick=4, ang=30, strut=5, wall=2, center=true);
-// Example: All Braces
-//   thinning_triangle(h=50, l=80, thick=4, ang=30, strut=5, wall=2, center=false);
-// Example: Diagonal Brace Only
-//   thinning_triangle(h=50, l=80, thick=4, ang=30, strut=5, wall=2, diagonly=true, center=false);
-module thinning_triangle(h=50, l=100, thick=5, ang=30, strut=5, wall=3, diagonly=false, center=undef, orient=ORIENT_Y, anchor=CENTER)
-{
-	dang = atan(h/l);
-	dlen = h/sin(dang);
-	size = [thick, h, l];
-	orient_and_anchor(size, orient, anchor, center=center, noncentered=BOTTOM+FRONT, orig_orient=ORIENT_Y, chain=true) {
-		difference() {
-			union() {
-				if (!diagonly) {
-					translate([0, 0, -h/2])
-						narrowing_strut(w=thick, l=l, wall=strut, ang=ang);
-					translate([0, -l/2, 0])
-						xrot(-90) narrowing_strut(w=thick, l=h-0.1, wall=strut, ang=ang);
-				}
-				intersection() {
-					cube(size=[thick, l, h], center=true);
-					xrot(-dang) yrot(180) {
-						narrowing_strut(w=thick, l=dlen*1.2, wall=strut, ang=ang);
-					}
-				}
-				cube(size=[wall, l-0.1, h-0.1], center=true);
-			}
-			xrot(-dang) {
-				translate([0, 0, h/2]) {
-					cube(size=[thick+0.1, l*2, h], center=true);
-				}
-			}
-		}
-		children();
-	}
-}
-
-
-// Module: sparse_strut()
-//
-// Description:
-//   Makes an open rectangular strut with X-shaped cross-bracing, designed to reduce
-//   the need for support material in 3D printing.
-//
-// Usage:
-//   sparse_strut(h, l, thick, [strut], [maxang], [max_bridge], [orient], [anchor])
-//
-// Arguments:
-//   h = height of strut wall.
-//   l = length of strut wall.
-//   thick = thickness of strut wall.
-//   maxang = maximum overhang angle of cross-braces.
-//   max_bridge = maximum bridging distance between cross-braces.
-//   strut = the width of the cross-braces.
-//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
-//
-// Example: Typical Shape
-//   sparse_strut(h=40, l=100, thick=3);
-// Example: Thinner Strut
-//   sparse_strut(h=40, l=100, thick=3, strut=2);
-// Example: Larger maxang
-//   sparse_strut(h=40, l=100, thick=3, strut=2, maxang=45);
-// Example: Longer max_bridge
-//   sparse_strut(h=40, l=100, thick=3, strut=2, maxang=45, max_bridge=30);
-module sparse_strut(h=50, l=100, thick=4, maxang=30, strut=5, max_bridge=20, orient=ORIENT_Y, anchor=CENTER)
-{
-	zoff = h/2 - strut/2;
-	yoff = l/2 - strut/2;
-
-	maxhyp = 1.5 * (max_bridge+strut)/2 / sin(maxang);
-	maxz = 2 * maxhyp * cos(maxang);
-
-	zreps = ceil(2*zoff/maxz);
-	zstep = 2*zoff / zreps;
-
-	hyp = zstep/2 / cos(maxang);
-	maxy = min(2 * hyp * sin(maxang), max_bridge+strut);
-
-	yreps = ceil(2*yoff/maxy);
-	ystep = 2*yoff / yreps;
-
-	ang = atan(ystep/zstep);
-	len = zstep / cos(ang);
-
-	size = [thick, l, h];
-	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
-		union() {
-			zspread(zoff*2)
-				cube(size=[thick, l, strut], center=true);
-			yspread(yoff*2)
-				cube(size=[thick, strut, h], center=true);
-			yspread(ystep, n=yreps) {
-				zspread(zstep, n=zreps) {
-					xrot( ang) cube(size=[thick, strut, len], center=true);
-					xrot(-ang) cube(size=[thick, strut, len], center=true);
-				}
-			}
-		}
-		children();
-	}
-}
-
-
-// Module: sparse_strut3d()
-//
-// Usage:
-//   sparse_strut3d(h, w, l, [thick], [maxang], [max_bridge], [strut], [orient], [anchor]);
-//
-// Description:
-//   Makes an open rectangular strut with X-shaped cross-bracing, designed to reduce the
-//   need for support material in 3D printing.
-//
-// Arguments:
-//   h = Z size of strut.
-//   w = X size of strut.
-//   l = Y size of strut.
-//   thick = thickness of strut walls.
-//   maxang = maximum overhang angle of cross-braces.
-//   max_bridge = maximum bridging distance between cross-braces.
-//   strut = the width of the cross-braces.
-//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
-//
-// Example: Typical Shape
-//   sparse_strut3d(h=30, w=30, l=100);
-// Example: Thinner strut
-//   sparse_strut3d(h=30, w=30, l=100, strut=2);
-// Example: Larger maxang
-//   sparse_strut3d(h=30, w=30, l=100, strut=2, maxang=50);
-// Example: Smaller max_bridge
-//   sparse_strut3d(h=30, w=30, l=100, strut=2, maxang=50, max_bridge=20);
-module sparse_strut3d(h=50, l=100, w=50, thick=3, maxang=40, strut=3, max_bridge=30, orient=ORIENT_Y, anchor=CENTER)
-{
-
-	xoff = w - thick;
-	yoff = l - thick;
-	zoff = h - thick;
-
-	xreps = ceil(xoff/yoff);
-	yreps = ceil(yoff/xoff);
-	zreps = ceil(zoff/min(xoff, yoff));
-
-	xstep = xoff / xreps;
-	ystep = yoff / yreps;
-	zstep = zoff / zreps;
-
-	cross_ang = atan2(xstep, ystep);
-	cross_len = hypot(xstep, ystep);
-
-	supp_ang = min(maxang, min(atan2(max_bridge, zstep), atan2(cross_len/2, zstep)));
-	supp_reps = floor(cross_len/2/(zstep*sin(supp_ang)));
-	supp_step = cross_len/2/supp_reps;
-
-	size = [w, l, h];
-	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
-		intersection() {
-			union() {
-				ybridge = (l - (yreps+1) * strut) / yreps;
-				xspread(xoff) sparse_strut(h=h, l=l, thick=thick, maxang=maxang, strut=strut, max_bridge=ybridge/ceil(ybridge/max_bridge));
-				yspread(yoff) zrot(90) sparse_strut(h=h, l=w, thick=thick, maxang=maxang, strut=strut, max_bridge=max_bridge);
-				for(zs = [0:zreps-1]) {
-					for(xs = [0:xreps-1]) {
-						for(ys = [0:yreps-1]) {
-							translate([(xs+0.5)*xstep-xoff/2, (ys+0.5)*ystep-yoff/2, (zs+0.5)*zstep-zoff/2]) {
-								zflip_copy(offset=-(zstep-strut)/2) {
-									xflip_copy() {
-										zrot(cross_ang) {
-											down(strut/2) {
-												cube([strut, cross_len, strut], center=true);
-											}
-											if (zreps>1) {
-												back(cross_len/2) {
-													zrot(-cross_ang) {
-														down(strut) cube([strut, strut, zstep+strut], anchor=BOTTOM);
-													}
-												}
-											}
-											for (soff = [0 : supp_reps-1] ) {
-												yflip_copy() {
-													back(soff*supp_step) {
-														skew_xy(ya=supp_ang) {
-															cube([strut, strut, zstep], anchor=BOTTOM);
-														}
-													}
-												}
-											}
-										}
-									}
-								}
-							}
-						}
-					}
-				}
-			}
-			cube([w,l,h], center=true);
-		}
-		children();
-	}
-}
-
-
-// Module: corrugated_wall()
-//
-// Description:
-//   Makes a corrugated wall which relieves contraction stress while still
-//   providing support strength.  Designed with 3D printing in mind.
-//
-// Usage:
-//   corrugated_wall(h, l, thick, [strut], [wall], [orient], [anchor]);
-//
-// Arguments:
-//   h = height of strut wall.
-//   l = length of strut wall.
-//   thick = thickness of strut wall.
-//   strut = the width of the cross-braces.
-//   wall = thickness of corrugations.
-//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
-//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
-//
-// Example: Typical Shape
-//   corrugated_wall(h=50, l=100);
-// Example: Wider Strut
-//   corrugated_wall(h=50, l=100, strut=8);
-// Example: Thicker Wall
-//   corrugated_wall(h=50, l=100, strut=8, wall=3);
-module corrugated_wall(h=50, l=100, thick=5, strut=5, wall=2, orient=ORIENT_Y, anchor=CENTER)
-{
-	amplitude = (thick - wall) / 2;
-	period = min(15, thick * 2);
-	steps = quantup(segs(thick/2),4);
-	step = period/steps;
-	il = l - 2*strut + 2*step;
-	size = [thick, l, h];
-	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
-		union() {
-			linear_extrude(height=h-2*strut+0.1, slices=2, convexity=ceil(2*il/period), center=true) {
-				polygon(
-					points=concat(
-						[for (y=[-il/2:step:il/2]) [amplitude*sin(y/period*360)-wall/2, y] ],
-						[for (y=[il/2:-step:-il/2]) [amplitude*sin(y/period*360)+wall/2, y] ]
-					)
-				);
-			}
-			difference() {
-				cube([thick, l, h], center=true);
-				cube([thick+0.5, l-2*strut, h-2*strut], center=true);
-			}
-		}
-		children();
-	}
-}
-
 
 // Section: Miscellaneous
 
diff --git a/transforms.scad b/transforms.scad
index 1dfdd03..2342672 100644
--- a/transforms.scad
+++ b/transforms.scad
@@ -459,7 +459,7 @@ module zflip(cp=[0,0,0]) translate(cp) mirror([0,0,1]) translate(-cp) children()
 //   Skews children on the X-Y plane, keeping constant in Z.
 //
 // Usage:
-//   skew_xy([xa], [ya]) ...
+//   skew_xy([xa], [ya], [planar]) ...
 //
 // Arguments:
 //   xa = skew angle towards the X direction.
diff --git a/walls.scad b/walls.scad
new file mode 100644
index 0000000..5977c6b
--- /dev/null
+++ b/walls.scad
@@ -0,0 +1,561 @@
+//////////////////////////////////////////////////////////////////////
+// LibFile: walls.scad
+//   Various wall constructions.
+//   To use, add the following lines to the beginning of your file:
+//   ```
+//   include <BOSL2/std.scad>
+//   include <BOSL2/walls.scad>
+//   ```
+//////////////////////////////////////////////////////////////////////
+
+/*
+BSD 2-Clause License
+
+Copyright (c) 2017-2019, Revar Desmera
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+
+// Section: Walls
+
+
+// Module: narrowing_strut()
+//
+// Description:
+//   Makes a rectangular strut with the top side narrowing in a triangle.
+//   The shape created may be likened to an extruded home plate from baseball.
+//   This is useful for constructing parts that minimize the need to support
+//   overhangs.
+//
+// Usage:
+//   narrowing_strut(w, l, wall, [ang], [orient], [anchor]);
+//
+// Arguments:
+//   w = Width (thickness) of the strut.
+//   l = Length of the strut.
+//   wall = height of rectangular portion of the strut.
+//   ang = angle that the trianglar side will converge at.
+//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `FRONT`.
+//
+// Example:
+//   narrowing_strut(w=10, l=100, wall=5, ang=30);
+module narrowing_strut(w=10, l=100, wall=5, ang=30, orient=ORIENT_Y, anchor=FRONT)
+{
+	h = wall + w/2/tan(ang);
+	size = [w, h, l];
+	orient_and_anchor(size, orient, anchor, chain=true) {
+		fwd(h/2) {
+			linear_extrude(height=l, center=true, slices=2) {
+				back(wall/2) square([w, wall], center=true);
+				back(wall-0.001) {
+					yscale(1/tan(ang)) {
+						difference() {
+							zrot(45) square(w/sqrt(2), center=true);
+							fwd(w/2) square(w, center=true);
+						}
+					}
+				}
+			}
+		}
+		children();
+	}
+}
+
+
+// Module: thinning_wall()
+//
+// Description:
+//   Makes a rectangular wall which thins to a smaller width in the center,
+//   with angled supports to prevent critical overhangs.
+//
+// Usage:
+//   thinning_wall(h, l, thick, [ang], [strut], [wall], [orient], [anchor]);
+//
+// Arguments:
+//   h = height of wall.
+//   l = length of wall.  If given as a vector of two numbers, specifies bottom and top lengths, respectively.
+//   thick = thickness of wall.
+//   ang = maximum overhang angle of diagonal brace.
+//   strut = the width of the diagonal brace.
+//   wall = the thickness of the thinned portion of the wall.
+//   orient = Orientation of the length axis of the wall.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_X`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
+//
+// Example: Typical Shape
+//   thinning_wall(h=50, l=80, thick=4);
+// Example: Trapezoidal
+//   thinning_wall(h=50, l=[80,50], thick=4);
+module thinning_wall(h=50, l=100, thick=5, ang=30, strut=5, wall=2, orient=ORIENT_Z, anchor=CENTER)
+{
+	l1 = (l[0] == undef)? l : l[0];
+	l2 = (l[1] == undef)? l : l[1];
+
+	trap_ang = atan2((l2-l1)/2, h);
+	corr1 = 1 + sin(trap_ang);
+	corr2 = 1 - sin(trap_ang);
+
+	z1 = h/2;
+	z2 = max(0.1, z1 - strut);
+	z3 = max(0.05, z2 - (thick-wall)/2*sin(90-ang)/sin(ang));
+
+	x1 = l2/2;
+	x2 = max(0.1, x1 - strut*corr1);
+	x3 = max(0.05, x2 - (thick-wall)/2*sin(90-ang)/sin(ang)*corr1);
+	x4 = l1/2;
+	x5 = max(0.1, x4 - strut*corr2);
+	x6 = max(0.05, x5 - (thick-wall)/2*sin(90-ang)/sin(ang)*corr2);
+
+	y1 = thick/2;
+	y2 = y1 - min(z2-z3, x2-x3) * sin(ang);
+
+	size = [l1, thick, h];
+	orient_and_anchor(size, orient, anchor, size2=[l2,thick], chain=true) {
+		polyhedron(
+			points=[
+				[-x4, -y1, -z1],
+				[ x4, -y1, -z1],
+				[ x1, -y1,  z1],
+				[-x1, -y1,  z1],
+
+				[-x5, -y1, -z2],
+				[ x5, -y1, -z2],
+				[ x2, -y1,  z2],
+				[-x2, -y1,  z2],
+
+				[-x6, -y2, -z3],
+				[ x6, -y2, -z3],
+				[ x3, -y2,  z3],
+				[-x3, -y2,  z3],
+
+				[-x4,  y1, -z1],
+				[ x4,  y1, -z1],
+				[ x1,  y1,  z1],
+				[-x1,  y1,  z1],
+
+				[-x5,  y1, -z2],
+				[ x5,  y1, -z2],
+				[ x2,  y1,  z2],
+				[-x2,  y1,  z2],
+
+				[-x6,  y2, -z3],
+				[ x6,  y2, -z3],
+				[ x3,  y2,  z3],
+				[-x3,  y2,  z3],
+			],
+			faces=[
+				[ 4,  5,  1],
+				[ 5,  6,  2],
+				[ 6,  7,  3],
+				[ 7,  4,  0],
+
+				[ 4,  1,  0],
+				[ 5,  2,  1],
+				[ 6,  3,  2],
+				[ 7,  0,  3],
+
+				[ 8,  9,  5],
+				[ 9, 10,  6],
+				[10, 11,  7],
+				[11,  8,  4],
+
+				[ 8,  5,  4],
+				[ 9,  6,  5],
+				[10,  7,  6],
+				[11,  4,  7],
+
+				[11, 10,  9],
+				[20, 21, 22],
+
+				[11,  9,  8],
+				[20, 22, 23],
+
+				[16, 17, 21],
+				[17, 18, 22],
+				[18, 19, 23],
+				[19, 16, 20],
+
+				[16, 21, 20],
+				[17, 22, 21],
+				[18, 23, 22],
+				[19, 20, 23],
+
+				[12, 13, 17],
+				[13, 14, 18],
+				[14, 15, 19],
+				[15, 12, 16],
+
+				[12, 17, 16],
+				[13, 18, 17],
+				[14, 19, 18],
+				[15, 16, 19],
+
+				[ 0,  1, 13],
+				[ 1,  2, 14],
+				[ 2,  3, 15],
+				[ 3,  0, 12],
+
+				[ 0, 13, 12],
+				[ 1, 14, 13],
+				[ 2, 15, 14],
+				[ 3, 12, 15],
+			],
+			convexity=6
+		);
+		children();
+	}
+}
+
+
+// Module: braced_thinning_wall()
+//
+// Description:
+//   Makes a rectangular wall with cross-bracing, which thins to a smaller width in the center,
+//   with angled supports to prevent critical overhangs.
+//
+// Usage:
+//   braced_thinning_wall(h, l, thick, [ang], [strut], [wall], [orient], [anchor]);
+//
+// Arguments:
+//   h = height of wall.
+//   l = length of wall.
+//   thick = thickness of wall.
+//   ang = maximum overhang angle of diagonal brace.
+//   strut = the width of the diagonal brace.
+//   wall = the thickness of the thinned portion of the wall.
+//   orient = Orientation of the length axis of the wall.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
+//
+// Example: Typical Shape
+//   braced_thinning_wall(h=50, l=100, thick=5);
+module braced_thinning_wall(h=50, l=100, thick=5, ang=30, strut=5, wall=2, orient=ORIENT_Y, anchor=CENTER)
+{
+	dang = atan((h-2*strut)/(l-2*strut));
+	dlen = (h-2*strut)/sin(dang);
+	size = [l, thick, h];
+	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
+		union() {
+			xrot_copies([0, 180]) {
+				down(h/2) narrowing_strut(w=thick, l=l, wall=strut, ang=ang);
+				fwd(l/2) xrot(-90) narrowing_strut(w=thick, l=h-0.1, wall=strut, ang=ang);
+				intersection() {
+					cube(size=[thick, l, h], center=true);
+					xrot_copies([-dang,dang]) {
+						zspread(strut/2) {
+							scale([1,1,1.5]) yrot(45) {
+								cube(size=[thick/sqrt(2), dlen, thick/sqrt(2)], center=true);
+							}
+						}
+						cube(size=[thick, dlen, strut/2], center=true);
+					}
+				}
+			}
+			cube(size=[wall, l-0.1, h-0.1], center=true);
+		}
+		children();
+	}
+}
+
+
+
+// Module: thinning_triangle()
+//
+// Description:
+//   Makes a triangular wall with thick edges, which thins to a smaller width in
+//   the center, with angled supports to prevent critical overhangs.
+//
+// Usage:
+//   thinning_triangle(h, l, thick, [ang], [strut], [wall], [diagonly], [orient], [anchor|center]);
+//
+// Arguments:
+//   h = height of wall.
+//   l = length of wall.
+//   thick = thickness of wall.
+//   ang = maximum overhang angle of diagonal brace.
+//   strut = the width of the diagonal brace.
+//   wall = the thickness of the thinned portion of the wall.
+//   diagonly = boolean, which denotes only the diagonal side (hypotenuse) should be thick.
+//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
+//   center = If true, centers shape.  If false, overrides `anchor` with `UP+BACK`.
+//
+// Example: Centered
+//   thinning_triangle(h=50, l=80, thick=4, ang=30, strut=5, wall=2, center=true);
+// Example: All Braces
+//   thinning_triangle(h=50, l=80, thick=4, ang=30, strut=5, wall=2, center=false);
+// Example: Diagonal Brace Only
+//   thinning_triangle(h=50, l=80, thick=4, ang=30, strut=5, wall=2, diagonly=true, center=false);
+module thinning_triangle(h=50, l=100, thick=5, ang=30, strut=5, wall=3, diagonly=false, center=undef, orient=ORIENT_Y, anchor=CENTER)
+{
+	dang = atan(h/l);
+	dlen = h/sin(dang);
+	size = [thick, h, l];
+	orient_and_anchor(size, orient, anchor, center=center, noncentered=BOTTOM+FRONT, orig_orient=ORIENT_Y, chain=true) {
+		difference() {
+			union() {
+				if (!diagonly) {
+					translate([0, 0, -h/2])
+						narrowing_strut(w=thick, l=l, wall=strut, ang=ang);
+					translate([0, -l/2, 0])
+						xrot(-90) narrowing_strut(w=thick, l=h-0.1, wall=strut, ang=ang);
+				}
+				intersection() {
+					cube(size=[thick, l, h], center=true);
+					xrot(-dang) yrot(180) {
+						narrowing_strut(w=thick, l=dlen*1.2, wall=strut, ang=ang);
+					}
+				}
+				cube(size=[wall, l-0.1, h-0.1], center=true);
+			}
+			xrot(-dang) {
+				translate([0, 0, h/2]) {
+					cube(size=[thick+0.1, l*2, h], center=true);
+				}
+			}
+		}
+		children();
+	}
+}
+
+
+// Module: sparse_strut()
+//
+// Description:
+//   Makes an open rectangular strut with X-shaped cross-bracing, designed to reduce
+//   the need for support material in 3D printing.
+//
+// Usage:
+//   sparse_strut(h, l, thick, [strut], [maxang], [max_bridge], [orient], [anchor])
+//
+// Arguments:
+//   h = height of strut wall.
+//   l = length of strut wall.
+//   thick = thickness of strut wall.
+//   maxang = maximum overhang angle of cross-braces.
+//   max_bridge = maximum bridging distance between cross-braces.
+//   strut = the width of the cross-braces.
+//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
+//
+// Example: Typical Shape
+//   sparse_strut(h=40, l=100, thick=3);
+// Example: Thinner Strut
+//   sparse_strut(h=40, l=100, thick=3, strut=2);
+// Example: Larger maxang
+//   sparse_strut(h=40, l=100, thick=3, strut=2, maxang=45);
+// Example: Longer max_bridge
+//   sparse_strut(h=40, l=100, thick=3, strut=2, maxang=45, max_bridge=30);
+module sparse_strut(h=50, l=100, thick=4, maxang=30, strut=5, max_bridge=20, orient=ORIENT_Y, anchor=CENTER)
+{
+	zoff = h/2 - strut/2;
+	yoff = l/2 - strut;
+
+	maxhyp = 1.5 * (max_bridge+strut)/2 / sin(maxang);
+	maxz = 2 * maxhyp * cos(maxang);
+
+	zreps = ceil(2*zoff/maxz);
+	zstep = 2*zoff / zreps;
+
+	hyp = zstep/2 / cos(maxang);
+	maxy = min(2 * hyp * sin(maxang), max_bridge+strut);
+
+	yreps = ceil(2*yoff/maxy);
+	ystep = 2*yoff / yreps;
+
+	ang = atan(ystep/zstep);
+	len = zstep / cos(ang);
+
+	size = [thick, l, h];
+	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
+		yrot(90)
+		linear_extrude(height=thick, convexity=4*yreps, center=true) {
+			difference() {
+				square([h, l], center=true);
+				square([h-2*strut, l-2*strut], center=true);
+			}
+			yspread(ystep, n=yreps) {
+				xspread(zstep, n=zreps) {
+					skew_xy(planar=true, ya=-ang) square([h-1.99*strut, strut], center=true);
+					skew_xy(planar=true, ya= ang) square([h-1.99*strut, strut], center=true);
+				}
+			}
+		}
+		children();
+	}
+}
+
+
+// Module: sparse_strut3d()
+//
+// Usage:
+//   sparse_strut3d(h, w, l, [thick], [maxang], [max_bridge], [strut], [orient], [anchor]);
+//
+// Description:
+//   Makes an open rectangular strut with X-shaped cross-bracing, designed to reduce the
+//   need for support material in 3D printing.
+//
+// Arguments:
+//   h = Z size of strut.
+//   w = X size of strut.
+//   l = Y size of strut.
+//   thick = thickness of strut walls.
+//   maxang = maximum overhang angle of cross-braces.
+//   max_bridge = maximum bridging distance between cross-braces.
+//   strut = the width of the cross-braces.
+//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
+//
+// Example: Typical Shape
+//   sparse_strut3d(h=30, w=30, l=100);
+// Example: Thinner strut
+//   sparse_strut3d(h=30, w=30, l=100, strut=2);
+// Example: Larger maxang
+//   sparse_strut3d(h=30, w=30, l=100, strut=2, maxang=50);
+// Example: Smaller max_bridge
+//   sparse_strut3d(h=30, w=30, l=100, strut=2, maxang=50, max_bridge=20);
+module sparse_strut3d(h=50, l=100, w=50, thick=3, maxang=40, strut=3, max_bridge=30, orient=ORIENT_Y, anchor=CENTER)
+{
+
+	xoff = w - thick;
+	yoff = l - thick;
+	zoff = h - thick;
+
+	xreps = ceil(xoff/yoff);
+	yreps = ceil(yoff/xoff);
+	zreps = ceil(zoff/min(xoff, yoff));
+
+	xstep = xoff / xreps;
+	ystep = yoff / yreps;
+	zstep = zoff / zreps;
+
+	cross_ang = atan2(xstep, ystep);
+	cross_len = hypot(xstep, ystep);
+
+	supp_ang = min(maxang, min(atan2(max_bridge, zstep), atan2(cross_len/2, zstep)));
+	supp_reps = floor(cross_len/2/(zstep*sin(supp_ang)));
+	supp_step = cross_len/2/supp_reps;
+
+	size = [w, l, h];
+	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
+		intersection() {
+			union() {
+				ybridge = (l - (yreps+1) * strut) / yreps;
+				xspread(xoff) sparse_strut(h=h, l=l, thick=thick, maxang=maxang, strut=strut, max_bridge=ybridge/ceil(ybridge/max_bridge));
+				yspread(yoff) zrot(90) sparse_strut(h=h, l=w, thick=thick, maxang=maxang, strut=strut, max_bridge=max_bridge);
+				for(zs = [0:zreps-1]) {
+					for(xs = [0:xreps-1]) {
+						for(ys = [0:yreps-1]) {
+							translate([(xs+0.5)*xstep-xoff/2, (ys+0.5)*ystep-yoff/2, (zs+0.5)*zstep-zoff/2]) {
+								zflip_copy(offset=-(zstep-strut)/2) {
+									xflip_copy() {
+										zrot(cross_ang) {
+											down(strut/2) {
+												cube([strut, cross_len, strut], center=true);
+											}
+											if (zreps>1) {
+												back(cross_len/2) {
+													zrot(-cross_ang) {
+														down(strut) cube([strut, strut, zstep+strut], anchor=BOTTOM);
+													}
+												}
+											}
+											for (soff = [0 : supp_reps-1] ) {
+												yflip_copy() {
+													back(soff*supp_step) {
+														skew_xy(ya=supp_ang) {
+															cube([strut, strut, zstep], anchor=BOTTOM);
+														}
+													}
+												}
+											}
+										}
+									}
+								}
+							}
+						}
+					}
+				}
+			}
+			cube([w,l,h], center=true);
+		}
+		children();
+	}
+}
+
+
+// Module: corrugated_wall()
+//
+// Description:
+//   Makes a corrugated wall which relieves contraction stress while still
+//   providing support strength.  Designed with 3D printing in mind.
+//
+// Usage:
+//   corrugated_wall(h, l, thick, [strut], [wall], [orient], [anchor]);
+//
+// Arguments:
+//   h = height of strut wall.
+//   l = length of strut wall.
+//   thick = thickness of strut wall.
+//   strut = the width of the cross-braces.
+//   wall = thickness of corrugations.
+//   orient = Orientation of the length axis of the shape.  Use the `ORIENT_` constants from `constants.scad`.  Default: `ORIENT_Y`.
+//   anchor = Alignment of the shape.  Use the constants from `constants.scad`.  Default: `CENTER`.
+//
+// Example: Typical Shape
+//   corrugated_wall(h=50, l=100);
+// Example: Wider Strut
+//   corrugated_wall(h=50, l=100, strut=8);
+// Example: Thicker Wall
+//   corrugated_wall(h=50, l=100, strut=8, wall=3);
+module corrugated_wall(h=50, l=100, thick=5, strut=5, wall=2, orient=ORIENT_Y, anchor=CENTER)
+{
+	amplitude = (thick - wall) / 2;
+	period = min(15, thick * 2);
+	steps = quantup(segs(thick/2),4);
+	step = period/steps;
+	il = l - 2*strut + 2*step;
+	size = [thick, l, h];
+	orient_and_anchor(size, orient, anchor, orig_orient=ORIENT_Y, chain=true) {
+		union() {
+			linear_extrude(height=h-2*strut+0.1, slices=2, convexity=ceil(2*il/period), center=true) {
+				polygon(
+					points=concat(
+						[for (y=[-il/2:step:il/2]) [amplitude*sin(y/period*360)-wall/2, y] ],
+						[for (y=[il/2:-step:-il/2]) [amplitude*sin(y/period*360)+wall/2, y] ]
+					)
+				);
+			}
+			difference() {
+				cube([thick, l, h], center=true);
+				cube([thick+0.5, l-2*strut, h-2*strut], center=true);
+			}
+		}
+		children();
+	}
+}
+
+
+
+// vim: noexpandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap