Yep, they have a metal sleeve/retainer that holds the lug on the back of the trim firmly in each hole. They are also sealed with normal garden variety body putty (usually non hardening and the same stuff that you use to seal the front window channel into the front door). This stops any water from entering the body and settling inside the lower guards. It is still readily available at parts stores but at a pinch you could get away with silicone based sealer but I would stay away from acidic cure silastic (use nuetral cure, in fact it is never a great idea to use anything with silicone in it anywhere near paint but sometimes you've got to....) as it will eventually etch through the paint and start acting on the metal surrounding the holes in the body.