Patching a body panel
From Crankshaft Coalition Wiki
 Patch panels
 Acquiring patch panels
There are a couple of ways you can acquire a patch panel to weld in.
- You can buy patch panels. This is not always an option if the vehicle you are working on isn't a popular model.
- You can fabricate your own patch panel.
- Make sure the panel/skin is in reasonable shape before you work on it; dents and formal repairs in the good part of the panel will distort the shape when the patch shape is cut out.
- Give yourself plenty of room with the patch; check if you can get behind the weld area.
- Cut the patch and then the panel, make sure both edges "match" together
- Clamp the panels and spot weld the panel in. Don't get it too hot.
- If possible, use TIG or gas, both produce a "soft" welds; MIG will work.
- Hammer weld the welds when hot (red). This stretches the weld; remember -- welding steel contracts the weld area.
- After spot welding, hammer and dolly the area to get it straight. Light off dolly work is best.
- Continue to weld in 3/4 length steps, don't get the area too HOT!
- Continue to hammer and dolly.
- Metal finish the area, use paint or large marker over area, block sand to find high/low spots. Hammer and dolly until there's little left.
- For best results use a shrinking disk on the imperfections, or use bondo.