Just use a magnet to hold your patch.... if that's what you're doing - and tack it in.
If you're hanging an entire panel - that's a job for clamps etc and there's usually somewhere you can get a clamp to hold the panel until you put a few tacks in it.
Just my experience is all.
If you're TIG welding -- make sure the magnets aren't near where you're attempting to weld -- TIG and magnets don't like each other.
