farmerdave said:We do?
Welding new metal in is the only real way to repair rust, anything else is a bog job. Are cars made of bog? Not many.
Good paint on a properly prepared surface is a pretty good start, also fixing leaks and water traps, goldseal type rustproofing and seamsealer help too.
But it isn't really worthwhile if you have another boot lid.
ofcourse car's aren't made of bog, for minor repairs bog is a much sounder, and safer soloution then new metal. Ofcourse if there was holes the size that you could poke your fingers into, etc.. you would have to replacer with metal, as bog, or fiberglass for that matter is simply not strong enough, but for minor repairs on areas that aren't going to get a lot of stress I would much rather use filler then new metal