(Rust repairs to Kim's FC floor)

So what is oxy hammer welding? Why did I leave a half inch overlap? This is a different car but the principal remains the same. Oxy hammer welding involves butt welding two panels together without overlap. Confused?. The overlap acts as a guide and supports the new pan - as the welding progress around the pan, the pan shrinks. The overlap is trimmed away just ahead of the oxyhammer welding using the 1mmm thick cut off wheel. A perfect gap is left for filling with welding wire. As an inch is welded- I call dolly and my assistant underneath the car places the dolly against the new hot weld and I hammer forge the two panels flat and even. This makes for a far neater job that can be controlled easily.