A worm shoe is a strip of wood such as oak or pine which is fixed to the keel of a wooden boat to protect it from shipworms. The wood is sacrificed to the worms while the main structure is kept separate and safe using a layer of tar paper or creosotedfelt, which the worms will not penetrate.
References
↑David MacLean (1977), Hauling Out and Winterizing, p.99, ISBN0830669442