Abstract: A method for interlocking the hemmed together flanges of the inner and outer panels comprises the steps of forming a plurality of raised beads at spaced intervals along the length of the edge of the inner panel; placing the inner panel inside the outer panel with the raised beads facing away from the outer panel; and hemming the edge of the outer panel over the edge of the inner panel by a hemming punch having a plurality of slots therein located to register with the raised beads of the inner panel so that the outer panel is coined into interlocking engagement with the raised beads to thereby interlock the inner and outer panels together against relative movement. The raised beads preferably have a height generally equal to the thickness of the inner panel, and are preferably elongated in shape with the elongation extending in the direction either parallel or perpendicular to the edge of the panel.