Abstract: Apparatus and a method of using it to straighten a dent in a sheet metal workpiece are provided. The apparatus includes a stud welding gun to releasably grip a stud and weld it to the dent, as well as integral hammer means to apply force to the welded stud, straightening the dent. The apparatus and the method of use then provide means for dewelding the stud from the straightened workpiece, thereby avoiding the usual stud cutting and grinding operations. Exchangeable electrodes are provided so that the apparatus can be used for both stud welding and spot welding.