diff --git a/readme.md b/readme.md
index c23ab3f..fcf0ac6 100644
--- a/readme.md
+++ b/readme.md
@@ -33,7 +33,7 @@ A list of changes classified as breaking, additions or fixes is maintained in [C
 <tr><td> <a href = "#box_sections">Box_sections</a> </td><td> <a href = "#magnets">Magnets</a> </td><td> <a href = "#screws">Screws</a> </td><td> <a href = "#drag_chain">Drag_chain</a> </td><td> <a href = "#layout">Layout</a> </td><td></td></tr>
 <tr><td> <a href = "#bulldogs">Bulldogs</a> </td><td> <a href = "#mains_sockets">Mains_sockets</a> </td><td> <a href = "#sealing_strip">Sealing_strip</a> </td><td> <a href = "#fan_guard">Fan_guard</a> </td><td> <a href = "#maths">Maths</a> </td><td></td></tr>
 <tr><td> <a href = "#buttons">Buttons</a> </td><td> <a href = "#microswitches">Microswitches</a> </td><td> <a href = "#servo_motors">Servo_motors</a> </td><td> <a href = "#fixing_block">Fixing_block</a> </td><td> <a href = "#offset">Offset</a> </td><td></td></tr>
-<tr><td> <a href = "#cable_strips">Cable_strips</a> </td><td> <a href = "#microview">Microview</a> </td><td> <a href = "#shaft_couplings">Shaft_couplings</a> </td><td> <a href = "#flat_hinge">Flat_hinge</a> </td><td> <a href = "#pcb_utils">PCB_utils</a> </td><td></td></tr>
+<tr><td> <a href = "#cable_strips">Cable_strips</a> </td><td> <a href = "#microview">Microview</a> </td><td> <a href = "#shaft_couplings">Shaft_couplings</a> </td><td> <a href = "#flat_hinge">Flat_hinge</a> </td><td> <a href = "#pcb_utils">Pcb_utils</a> </td><td></td></tr>
 <tr><td> <a href = "#cameras">Cameras</a> </td><td> <a href = "#modules">Modules</a> </td><td> <a href = "#sheets">Sheets</a> </td><td> <a href = "#foot">Foot</a> </td><td> <a href = "#quadrant">Quadrant</a> </td><td></td></tr>
 <tr><td> <a href = "#circlips">Circlips</a> </td><td> <a href = "#nuts">Nuts</a> </td><td> <a href = "#spades">Spades</a> </td><td> <a href = "#handle">Handle</a> </td><td> <a href = "#round">Round</a> </td><td></td></tr>
 <tr><td> <a href = "#components">Components</a> </td><td> <a href = "#o_ring">O_ring</a> </td><td> <a href = "#spools">Spools</a> </td><td> <a href = "#knob">Knob</a> </td><td> <a href = "#rounded_cylinder">Rounded_cylinder</a> </td><td></td></tr>
@@ -4012,6 +4012,8 @@ When woven sheets (e.g. carbon fibre) are rendered it is necessary to specify th
 |   1 | `sheet(MDF10, 30, 30, 2)` |  Sheet MDF 30mm x 30mm x 10mm |
 |   1 | `sheet(MDF12, 30, 30, 2)` |  Sheet MDF 30mm x 30mm x 12mm |
 |   1 | `sheet(MDF19, 30, 30, 2)` |  Sheet MDF 30mm x 30mm x 19mm |
+|   1 | `sheet(MDF22, 30, 30, 2)` |  Sheet MDF 30mm x 30mm x 22mm |
+|   1 | `sheet(MDF3, 30, 30, 2)` |  Sheet MDF 30mm x 30mm x 3mm |
 |   1 | `sheet(MDF6, 30, 30, 2)` |  Sheet MDF 30mm x 30mm x 6mm |
 |   1 | `sheet(PMMA1p25, 30, 30, 2)` |  Sheet acrylic 30mm x 30mm x 1.25mm |
 |   1 | `sheet(PMMA10, 30, 30, 2)` |  Sheet acrylic 30mm x 30mm x 10mm |
@@ -7150,12 +7152,12 @@ If `chamfer_base` is true then the bottom edge is made suitable for 3D printing
 
 ---
 <a name="pcb_utils"></a>
-## PCB_utils
+## Pcb_utils
 Utilities for making PCBs and components
 
 [utils/pcb_utils.scad](utils/pcb_utils.scad) Implementation.
 
-[tests/PCB_utils.scad](tests/PCB_utils.scad) Code for this example.
+[tests/pcb_utils.scad](tests/pcb_utils.scad) Code for this example.
 
 ### Modules
 | Module | Description |
diff --git a/tests/png/sheets.png b/tests/png/sheets.png
index 447b307..1df19b4 100644
Binary files a/tests/png/sheets.png and b/tests/png/sheets.png differ
diff --git a/vitamins/sheets.scad b/vitamins/sheets.scad
index e130261..d1681da 100644
--- a/vitamins/sheets.scad
+++ b/vitamins/sheets.scad
@@ -26,11 +26,13 @@
 //
 mdf_colour = "#BEA587"; // sampled from a photo
 
+MDF3      = [ "MDF3",      "Sheet MDF",               3, mdf_colour,             true];
 MDF6      = [ "MDF6",      "Sheet MDF",               6, mdf_colour,             true];    // ~1/4"
 MDF10     = [ "MDF10",     "Sheet MDF",              10, mdf_colour,             true];    // ~3/8"
 MDF12     = [ "MDF12",     "Sheet MDF",              12, mdf_colour,             true];    // ~1/2"
 MDF18     = [ "MDF18",     "Sheet MDF",              18, mdf_colour,             true];
 MDF19     = [ "MDF19",     "Sheet MDF",              19, mdf_colour,             true];    // ~3/4"
+MDF22     = [ "MDF22",     "Sheet MDF",              22, mdf_colour,             true];
 PMMA1p25  = [ "PMMA1p25",  "Sheet acrylic",         1.25,[1,   1,   1,   0.5  ], false];
 PMMA2     = [ "PMMA2",     "Sheet acrylic",           2, [1,   1,   1,   0.5  ], false];
 PMMA3     = [ "PMMA3",     "Sheet acrylic",           3, [1,   1,   1,   0.5  ], false];   // ~1/8"
@@ -56,7 +58,7 @@ CF2 =       [ "CF2",       "Sheet carbon fiber",      2, grey(35),
 CF3 =       [ "CF3",       "Sheet carbon fiber",      3, grey(35),               false,  2,  2,  grey(20)];
 
 
-sheets = [CF1, CF2, CF3, MDF6, MDF10, MDF12, MDF19, PMMA1p25, PMMA2, PMMA3, PMMA6, PMMA8, PMMA10,
+sheets = [CF1, CF2, CF3, MDF3, MDF6, MDF10, MDF12, MDF19, MDF22, PMMA1p25, PMMA2, PMMA3, PMMA6, PMMA8, PMMA10,
          glass2, DiBond, DiBond6, Cardboard, FoilTape, AL1_6, AL2, AL3, AL6, AL8, Steel06, Spring08, Silicone3, Foam20];
 
 use <sheet.scad>