Prusa i3 ANET A8, Z Endstop Adjuster.

thingiverse

Update: Allow use of optical endstop. After having to rely on a poorly designed Z stop adjust for far too long, I've finally come up with a mod that combines elements from various other projects here. To start, remove the two left bolts from the LHS Z motor and place the motor mount over it. Next, replace the old bolts with ones that are 2mm longer (M3 x 12mm). Attach the micro switch to the mount using two M2 14mm bolts and nuts. I used a bit of locktite in the correct spot once, but you can skip that step if you prefer. On the adjuster, there's a cutout for an M4 nut. It's a very tight fit, so be prepared to file out or use a soldering iron to get it to fit properly. Once the nut is fitted, thread a M4 bolt/screw through it. For added security, I also attached another nut as a locknut. Now lower the Z axis down slowly towards the micro switch and make sure everything lines up perfectly. Finally, tighten the micro switch in place with the M2 bolts and nuts. Good luck!