Squareness comparator. By Woods Creek Workshop.
16:11 video:
https://www.youtube.com/watch?v=KiggIk43ejk
24:16 video:
https://www.youtube.com/watch?v=60lGfMbeNbI
Previously:
https://www.homemadetools.net/forum/...413#post142601
https://www.homemadetools.net/forum/...978#post153059
