Screw you

Get your minds out of the gutter - I'm talking about a nautical screw, ya lubbers.

It's from the scrap pile of the shipyard I wrote about in this post and this post. It's bronze, about 9 inches, with a 3 inch pitch. They still make 'em like this - bronze is resistant to corrosion in salt water, and because it's not as hard as steel, it deforms on impact (thereby saving shafts and engines as well as making them easier to bang into shape in the field as a temporary repair until one can get to a proper boatyard).