Mendel microswitch/opto holder in OpenSCAD w nut traps

This is a modification of the Y bar clamps, and comes with a shelf sticking out of it to stick optical or mechanical limit sensors on. It clamps onto 8mm or 5/16\" rod for those who still work in old money.

The idea is that non-standard endstop mechanisms can be stuck to the shelf, allowing experimentation with microswitches etc.

There is also a part equivalent to the PCB spacer in the standard Mendel that is used to close the clamp after it is attached to the bar (doesn\'t show well in th