Back in the day, on repairs that you can’t access to be beaten out would have had holes drilled and screws attached before pulling the dent, the problem with this is that there would be holes in the metal, fillers are puros and in comes the rot under the repair.

Nowadays the use of copper pins are a must, using a pin welder copper pins are welded on to the damaged area, a slide puller attached to the pins and the pins then pulled until the desired shape is achieved, the pins are then snapped off and ground flat, the end result is the metal isn’t punctured and the repair can be completed with confidence and without the risk of corrosion forming underneath.