diff --git a/src/maze/_impl/_mz_comm.scad b/src/maze/_impl/_mz_comm.scad
index 60dcff2c..acc258dc 100644
--- a/src/maze/_impl/_mz_comm.scad
+++ b/src/maze/_impl/_mz_comm.scad
@@ -2,6 +2,7 @@
 // TOP_WALL = 1;    
 // RIGHT_WALL = 2;    
 // TOP_RIGHT_WALL = 3; 
+// MASK = 4;
 
 function no_wall(block) = get_wall_type(block) == 0;
 function top_wall(block) = get_wall_type(block) == 1;