Just put a set on a '55 Ford for a customer. He picked them up somewhere, but they appeared aftermarket by the hardware. There is a center, L shaped bracket that grabs the wheel lip top center, pulled tight by a bolt from the bottom of the skirt. Front and rear there are bracket type clamps that grab the wheel lip with a bolt and nut that fit through a slotted hole in the skirt. As you tighten those bolts, the clamps tighten on the wheel lip, holding the skirt in place.