Felt

Matted fibrous material, produced in rolls and sheets, and used to place between sheathing of copper, yellow-metal, zinc, or wood, and the outside-planking of a ve el; serving (to a slight extent at least) in preventing water entering the seams under such sheathing in case of their becoming leaky; also as some protection from the sea-worm, when any portion of the sheathing gets lost during the voyage.