I've got an 86 F-150 stepside with a tonneau cover on it. When I put in all the screws in the bed I put some 3M calkstrip stuff on the threads of the screws to try to seal out moisture, but there are two sets of holes in the front of the bed, and I only need one. It dosn't have to look pretty or be paintable, I just need it to keep water out. Should I use more calkstrip/dumdum stuff, or rtv silicone? Something else? Maybe something to put back around the snaps too? Any tips? thanks!

 

I have had pretty good luck with seam sealer!