The roof panels have a gentle curvature that makes it impossible to use a flat sheet of steel to replace the factory insert. Skill and experience enable Bobby to know just how to form the panels using a Yoder power hammer. Wanna know the secret? Then sign up for one of Bobby's sheetmetal-shaping seminars. Sedan roof panels are made in two halves owing to their physical size, as they're simply too large to form in one piece. Bobby trial-fit the second half of Dale Brooks' '34 sedan panel on the buck. It may take a few trial-fittings before Bobby is happy with the panel. You can see the curvature of the panel clearly here.