I agree with one of the other reviewers - they are definitely not for precision work. Too bad, because otherwise they are very cute. The aluminum is 3/4 inch thick or more, the machining and finish is good, and the hardware is good. But I have one clamp that's square as hell and the other one that's square as hell...not square. I've tried clamping it in a vise and hitting it with a hammer, but no matter how thick they are I don't think you can straighten them. without hydraulic equipment. I recommend looking elsewhere if you're making picture frames and the like.