Reviews claiming that the measurement scale is "offset" are incorrect - they are calibrated to the outside edges of the squares. Reviews that claim the angles aren't 90 degrees are wrong - I've tested them with two calibrated Woodpeckers squares (1812 and 2616) and they're exactly 90 degrees within the tolerances of those squares. I wish these squares were a bit thicker to make them easier to use with regular bar clamps.