The rudder's main purpose is to

• A. To measure depth
• B. To anchor the ship
• C. To provide propulsion
• D. To steer the ship

Answer: (D)

Steering the vessel is the rudder’s primary role. The rudder is a movable blade at the stern that deflects water as the ship moves. When you turn the rudder to one side, the redirected water creates a sideways force that causes the ship to yaw, changing its course. The helm sets the desired direction, and the steering gear moves the rudder to the corresponding angle; the turn’s sharpness depends on the rudder angle and the ship’s speed. This function is distinct from depth measurement, anchoring, or propulsion, which are handled by other systems: depth is measured with depth-sounding equipment, the anchor system deploys or retrieves the anchor, and propulsion comes from the engines and propellers.