A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other conveyance that moves through a fluid medium. On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to …
Modern ship rudder (the long red rectangle behind the propeller)
Stern-mounted steering oar of an Egyptian riverboat depicted in the Tomb of Menna (c. 1422-1411 BC)
Steering oar of a Roman boat, 1st century AD (RG-Museum, Cologne).
An early Song Dynasty (960–1279) painting on silk of two Chinese cargo ships accompanied by a smaller boat, by Guo Zhongshu (c. 910–977 AD); notice the large sternpost-mounted rudder on the ship shown in the foreground