The keying could be created on the inside, so there is no need for the
additional space above the ring.
thickness = 2;
ring_height = thickness;
-ring_pos = thickness;
+ring_pos = 0;
ring_clearance = ring_height + ring_pos;
ring_thickness = thickness / 2;
linear_extrude(ring_height)
difference()
{
- square([width, depth], center=true);
+ square([width, depth], center = true);
square([width - 2 * ring_thickness, depth - 2 * ring_thickness], center = true);
};
}