The Kossel deltabot by Johann uses rods with Traxxas rod ends. These rod ends can have sloppy tolerances, and this Thing provides an accurate way to measure the backlash of the ball within the ball joint, using a dial test indicator.Just print it, insert the dial test indicator, insert the rod end, and then check the backlash when you push against the rod end ball. I used a ball-end allen wrench and it worked perfectly. Printed w/0.4mm layers, 0.5mm nozzle, and 0.25 infill using Slic3r 0.9.8. The .stl was run through NetFabb; if you change the OpenScad source, make sure to do this, or you'll get a solid block from the slicer.Note that the file has some holes that were meant to help lock in the rod end and the dial test indicator. These are sized to be tapped for 6-32 screws. I found that the press fit was fine.