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 the STL image).Clamp around bar and do up 2 off M4x40 with washers and trapped nuts spaced diagonally. Glue optical or mechanical sensor to platform with hotmelt glue or epoxy. Ensure it lines up with the sensor\'s activator!I tend to use small, lever-action microswitches and solder them to a bit of board. The board carries a connector and a 100K resistor (brown-black-yellow) to limit current through the switch when it connects to either 5V or the ground rail.