A common find during the process is unearthing a previous repair. Years ago, body shops would typically drill holes and use slide hammers to pull dents from sheetmetal. Then the holes would be filled with plastic body filler and sanded smooth. Today, a Stud Welder System spot-welds pins to the surface of the metal that are then grasped with a special puller to remove the dent without drilling holes. Making modern repairs to this type of discovery is one of the reasons it's a good idea to strip a car to bare metal prior to a quality restoration.