Without using several pairs of these, at varied lengths, I would be forced to actually do measurements with an often misread tape measure. Something everyone would benefit from having. Set them to touch between 2 points, and they remain constant until you change them. Check and recheck cross angles for square, widths, depths, and lengths. Any measurement between 2 points.

Great post Rick, these are something I think many are unaware of, and yours fit the description to a T.