This is a simple, homemade clamp that is very effective for holding large panels securely, providing the precise alignment and rigidity needed for butt-welding. I do a lot of top chops, hood pie ...
It’s a workshop axiom: If you can’t hold the workpiece securely, you can’t work on it well. Sure, there are lots of times when you can hold something with one hand and cut or drill it with the other.