This is a tool for aligning turntable cartridges. It is sized for a tonearm with an effective length of 221mm, a common size used by Pioneer and many other manufacturers.

The geometry used is "Lofgren A" with null points at 66mm at 120.89mm, calculated using the resources on vinylengine.com.

There are two small square lugs on the back edge of the jig. The outside edges of these lugs should be exactly 100mm apart. Print the file at 100% scale, then use calipers to measure the outside edges of the lugs. If the measurement is not 100mm, adjust the printing scale and reprint.