Making and using a squareness comparator, with tips and tricks along the way, plus some history and metrology - part 2. I have put the CAD file as DFX on the CNC Zone thread to save you CAD time. https://www.cnczone.com/forums/tormach-personal-cnc-mill/417078-tormach-project-squareness-comparator.html#post2438284
