The holders in this design are clipped onto the rods and frame of the Prusa i3 to provide firm but easily-moved mounting points for the Y and Z axis endstops. The Z axis endstop holder includes a variation with a front-accessible adjuster. The adjuster part can be printed with any amount of extra height by modifying the parameters in its SCAD file.

Adjustable Z Holder

The Z adjuster requires the endstop holder to be printed sideways with bridging, so the endstop fit may be tight. Also, the sliding block part may be fragile, so be careful when assembling. By default the adjuster can move over a range of ~2.5mm.

To assemble, first raise the Z axis to get the gantry out of the way. Then, clip on the Adjuster. Next, clip on the Holder (with endstop inserted) leaving ~1cm of space between it and the Adjuster. (Run the endstop wires under the Adjuster.) Insert an M3 nut into the nut trap in the Slider, and insert the Slider into the tab on the Holder. Slide the Holder down until the Slider is resting in the Adjuster Block. Put the M3x20mm screw through the Adjuster Block and Slider and tighten until the screw is all the way in. Put 2 x M3 nuts on the end of the screw to keep it in place. The adjuster can be optionally attached at the back of the frame with a short tack or screw.

Results so far...

I've tested the Adjustable Z Holder in PLA. It works great, and the fit is definitely tight. During assembly parts of the sliding block tab and holder broke off due to weak layer adhesion, but it didn't affect the functionality of the part at all. I also had to heat up the M3 nut to melt it down into the nut trap. The holder can afford to be a lot looser, while printing in ABS should yield all 'round stronger parts. A future revision will hopefully produce stronger PLA parts too.