If it's screws that go into wood, you can wax the screw and put some neat epoxy down into the screw hole. It will seal the wood and form a set of threads around the screw. For this technique, you do not wait for the epoxy to harden.
If it's a through bolt, you can still seal the hole with epoxy (neat, no fillers). Or you can overdrill the hole, fill it with epoxy stuffed with strands of glass and then redrill the correct size after the epoxy has cured.
All those techniques will seal the wood.