Vane

1. Rotating device which is used to indicate direction of wind. Also called wind or weather vanes. 2. Flat surface that rotates pushing against air or water. 3. Fins that stabilize a towed or dropped object. The otter boards that hold a otter trawl open are vanes. 4. The sighting devices on a backstaff or other nautical instrument based on the derivation of vanes as pieces that stick out at 90 degrees from an axis.