Welding up holes

After searching the internet I came across a neat little trick that works really well. I place a peice of copper behind the hole I am filling in with my M.I.G, so that when im welding the copper helps to stop the thin steel from blowing out. The steel will not stick to the copper so when I am done the weld is already flat on the face that the copper was held against.

I got two of these from the bargin bin at bunnings for $5. I think they were ment to be replacment parts for a hammer with copper ends.