Many boatbuilders, especially those near salt water, prefer a screw with a full-body diameter shank. Unlike the reduced shank of a typical roll-threaded screw (like most of the screws we carry), the full-body diameter shank completely fills the clearance (or body) hole boatbuilders usually drill in the first board. This creates a rather good seal as water swells the wood, and also helps prevent the rot that may result from the trapped moisture. At one time, all screws had machine-cut threads and a shank diameter equal to the outside diameter of the screw thread. Modern high-speed screw-making equipment produces an extruded thread screw with a reduced shank diameter, and has largely eliminated the slower-to-produce cut thread screw many boatbuilders prefer.

	Reduced Shank Roll-Threaded Screw	Full Body Shank Boatbuilding Screw