#6 Flat head slotted bronze wood screws. Traditional boatbuilders love these Silicon Bronze wood screws because they have cut threads and the full-bodied diameter shank. Unlike rolled thread screws with their reduced shank, these screws have a shank diameter that is the same size as the outside of the threads. This completely fills the clearance hole normally drilled for the shank thus creating a waterproof seal. Remember to drill a body hole for the screw shank and a pilot hole for the threads. All screws are threaded for 2/3 of the shank.