The pad is a spring or air operated plate used in forming dies. The pad is used to grip the sheet metal against the punch or die steel. The functions of the pad are as follows: 1- To hold the sheet metal in proper location during forming. 2- To hold the sheet metal flat. During forming, the areas not being formed tend to bow or otherwise distort. Therefore, these areas are held in their original contour by pad pressure. 3- The pad acts as a hold-down.” (Eary, D. F., & Reed, E. A., 1958, p. 306-308).
Source: The OHIO State University