fin boxes and leash plugs

lets say i want to put in a fin box on my board. how do i get a clean cut through the stringer? same goes for a leash plug that sits on the stringer…

Router, go slow.

…and not the it matters, but if you’re using a box, and would rather have a clean look to the deck, rather than cutting an ugly leash cup in there, consider drilling through the box. i hate leash cups.