very nice tools for making square corners. different from the magnet type in that you don't get the SNAP of the magnets coming together. with these you can gradually apply clamping force.

This is a good tool but it doesn't really work when one of the walls is angled at the top, like those supporting an angled roof. I end up using them on the bottom edge, where things are square, then find some other method to get the top angle square - such as using magnetic roof clamps set at a right angle.