Here is the correct way to install a deckfill (well, correct way according to us).
- From the underside, spot the center of the (future) deckfill, and drill a pilot hole.
- From the topside, grind away the nonskid surrounding the pilot hole (optional, but not for us as the deck here has quite aggressive nonskid. We will be refinishing the decks in the future).
- From the topside, cut a hole with a holesaw just large enough to fit the body of the deckfill. Carbide grit holesaws work best on fiberglass.
- Rabbet out any core, at least a half inch, with a small router and rabbeting bit.
- Fill the rabbet with thickened epoxy or filler. Be sure to prime the inside surface with catalyzed resin that is compatible with your filler of choice. This will prevent any moisture possibly leaking and absorbing into the deck core.
- Once cured, grind/sand the filler to smooth out the inside edges of the hole. A power drill with a small drum sander bit works good.
- Test fit the deckfills, make sure they drop in easily and are centered and positioned (In this case, the text is oriented such that it is readable from the dock).
- Mark screw hole centers with a sharpie.
- Drill an oversized hole on the hole centers. These should at least be twice the size of the mounting screws.
- Epoxy plug the oversized holes. (as with the rabbet above, this is to prevent water ingress into the core)
- Once cured, re-mark the hole centers from the deckfill and drill pilot holes for each screw.
- Apply sealant, drop in the deckfill, and screw it down.
- Once the sealant has cured, trim away excess with a razor.
In our case, we initially used light duty sealant as we will need to temporarily remove these when it comes time to refinish the decks.
More pictures in the "Latest Activity" slideshow in the sidebar.