Cap screw washer for 1/4" hex head cap screws

thingiverse

I used these washers to attach the roof of my pop-up camper (1996 Starcraft) to the supports. Place the washer on the cap screw. Apply a bead of caulk around the bolt hole. Insert bolt. A groove on the underside allows a place for excess caulk to create a better seal. The tapered exterior gives a great finished look.