When I started following MP&C's advise to make the patch as tight as possible I saw cleco's would leave a gap which doesn't help the blow outs any... So the old speaker magnets I had laying around held things nice and tight.
I've also taken to laying a this strip of copper sheet between the mag and the back side of the weld to help prevent blow outs on thin metal or when filling holes.
Another really handy use is installing nuts and bolts on the bed. Drop the bolt through, set the mag on it and then move underneath and slip the washers on one at a time, grab the nut and start it..
