I think you are describing the hole for the diagonal rod brace. The topside is a welded square nut to a 1/2x2" strip of metal indented into the pan. On the bottom a 8-10" rod with flattened, drilled ends is attached. The rod leads to the bottom valance and fender. There is a metal stiffener bar there where all the panels and the rod meets. If that's not it, I'm clueless too.
