FILLING SMALL HOLES
Sometimes panels have a few small holes where rust has eaten through, but patches would be too fiddly or inappropriate. A poorly-publicised, but most useful tip is to hold or clamp a piece of flat copper behind the hole as you fill it with weld from the front. It stops the fill metal dropping through and, being copper, the weld metal doesn't stick to it. It also takes away some of the excess heat, so it prevents the edge melting too easily. Only the side you were filling from will need any significant amount of grinding, so weld from the side you can grind off more easily, which will probably be the one you can weld easier anyway!
A commercial tool is available, but a DIY version can easily be made from a short length of copper water pipe, to which a piece of wooden dowel has been pinned. The pipe is flattened together, and can then be hand-held or clamped behind the hole, as appropriate. You may need to cool it from time to time to stop the handle smoking, but it really does work well!
© VW Type 3 & 4 Club; October 1997