Sheet Metal and Non-Metallic Structures If a streamline cover plate is to be hand formed using a form block, a piece of dead soft aluminum should first be placed over the hollow portion of the mold and securely fastened in place. The bumping operation should be a. distributed evenly over the face of the aluminum at all times rather than being started at the edges or center. b. started by tapping the aluminum lightly around the edges and gradually working down into the center. c. started by tapping the aluminum in the center until it touches the bottom of the mold and then working out in all directions.