Can you give us a link?
'50s GM cars had a rubber flap that ran the width of the vehicle, between the tail panel and the bumper. It kept dust and grime from getting up between the bumper and the panel. There was a U-channel stamped into the panels, and the bottom of the back of the quarter panels, the rubber went into it from the top, and the channel was crimped closed/pinched with a hammer to hold the rubber in place.
My '62 Suburban has a similar rubber seal, though it uses a sheetmetal strip that screws to the tail panel, sandwiching the gasket between it and the body.
Installed, the rubber goes toward the sky, and is folded over to tuck up behind the bumper. It doesn't just hang down.
-Brad
