Answer: leeboard

AnswerCrossword Clue
LEEBOARDMovable plank on a hull
LEEBOARDSailboat appurtenance.
LEEBOARDNavigational aid on a sailboat
leeboarda board attached to a sailing vessel to prevent leeway
leeboardeither of two broad, flat objects attached to the sides of a sailing ship amidships, the one on the lee side being lowered into the water to prevent the ship from making leeway