This is a remix of thing #335726 by greymatterdroppings (Matt). It is an adjustable, configurable Y endstop holder.
It can be adjusted for height and depth allowing for precise adjustment of the Y home position, and it can be configured for use with either any Prusa i3 variant with 8mm rods (e.g. the Prusa i3 vanilla or the improved Twelvepro Prusa i3), or the P3Steel. Also, the limit switch is attached to a small carrier and two carrier choices are possible: either the Makerbot a.k.a Sainsmart mechanical switch, or a plain miniature limit switch.
OpenSCAD sources (with proper attribution to Matt) are included so this part can be edited to taste.
No bridges! Can be printed in ABS or PLA. 35% infill works for me and results in strong parts. Requires 1 x M3 12mm hex bolt and nyloc nut for the P3Steel mount. Requires 4 x M3 16mm or 20mm bolts, washers and nyloc nuts for the adjustable parts. Requires a nylon zip tie or 2 x M3 12mm bolts and nyloc nuts depending on carrier choice.