1967 Dodge Dart GT Convertible

Are you talking about the rocker molding or the top of fender/door trim

The top of fender trim uses a small o ring to seal. The post goes into the hole, then a pin spreads the post to lock it into the hole.

The rocker has a top hat shaped rubber seal that fits over the prongs on the clip that go thru the holes in the rockers. When you pinch the prongs on the outside of the clip it spreads the prongs in the rubber and locking it in the hole. Alternately you could use a screw to attach each clip to the body and fill the hole with dumb dumb