SeaSense Patented one way safety plug lets water out of your bilge but not back in! Ideal for every boater who has ever forgotten to put in the plug. 1/2" NPT. Features our exclusive EZ-IN Garboard Plug. Our EZ-IN Garboard Plug features our exclusive plug handle which allows the plug to be tightened and loosened with a wrench, screwdriver or even a nail! 1/2" NPT female plug.