[Andy White]

Ensure that the metal to be welded is very clean, free of paint, underseal, rust, oil, etc. If the area to be welded has any surface rust on it, it is easiest to remove it first with a wire wheel on your angle grinder.

You can buy a tool called a joggler to make repairs in hidden areas easier. It creates a step in the metal for your repair panel to sit into. Alternatively and my prefered method is to butt weld the panels together. You must take your time and make sure that the repair piece fits perfectly. A small amount of time carefully filing or angle grinding the metal down for a perfect fit will result in a good job.

Ensure your welder has a good earth! Start with the corners and tack the panel in place. A tack should take no more than a couple of seconds and should sound like frying bacon. Check everything is still aligned whilst it is possible to break the tacks.

Take your time. No more than six spot welds at a time and allow to cool. That way you will end up with minimal heat distortion and filler.

Good Luck!

Andy.