--- /dev/null
+// -*- C -*-
+
+circle_inner_rad = 10;
+
+thick = 3;
+
+tab_sz = 15;
+
+// calculated
+
+circle_outer_rad = circle_inner_rad + thick;
+
+module Plan() {
+ difference(){
+ circle(r=circle_outer_rad);
+ circle(r=circle_inner_rad);
+ mirror([1,0]) square([50,50]);
+ }
+ translate([-circle_outer_rad, -0.1])
+ square([thick, tab_sz + circle_outer_rad]);
+}
+
+Plan();