This plug can be used if needed by plugging the thru-hull from the outside to allow full disassembly of the valve to clear a clog or replace the entire body all without having to haul the boat.
I have four thru-hulls with four of these seacocks attached to them. They're 17 years old and the first one started leaking. I pulled it out and replaced it with a new Forespar Seacock and then rebuilt the original one and will carry it as a spare. These seacocks are outstanding!