This y-endstop is attached to the rear (or front) threaded rods of a Mendel type printer, e.g. by inserting its base between a vertex or rod clamp and its corresponding screw net. The endstop consists of a fixed base and a sliding arm onto which the endstop switch is mounted. The length of the slide and the position (horizontal/vertical) of the switch are configurable. The endstop can be mounted without disassembling the rods. It is stuck onto the lower threaded rod and then rotated along the circular cavity into the upper rod. The extension to the lower rod stabilizes the rotational position the the endstop so that it won't rotate unintentionally around the upper rod. The switch holders have several screw hole slots that fit the standard 20x6mm micro-switches, which have screw holes which are spaced by 9.5mm. I found it easiest to extend the 2mm holes with a 2.5mm drill bit and then cut an M3 thread into them (using an M3 tap or just with a clean cut M3 screw). The STL files provided are for a standard sized Mendel (or any variant thereof, as is the Air-like version I use), which have M8 front and rear threaded rods that are spaced by 58.5mm at an angle of 60 degrees. For other dimensions, you need to modify the included SCAD file, where these parameters are parametrized. Note that for Prusa i3 type printers, you should use my sliding i3 Y-endstop. I only include STL files for a few versions of the sliding arm. More variations can be found on my sliding X-endstop or the above mentioned sliding i3 Y-endstop, which both use compatible sliding arms.