Rudder

1. A vertically hinged plate of metal, fiberglass, or wood mounted at the stern of a vessel for directing its course. A rudder operates by redirecting the fluid past the hull, thus imparting a turning or yawing motion to the craft.
2. A similar structure at the tail of an aircraft, used for effecting horizontal changes in course. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.