A rudder is a primary vertical steering fin attached to the stern (rear) of a boat, allowing the helmsman to control direction by deflecting water flow. Connected to a tiller or wheel, it creates pressure differences that turn the vessel. It is essential for maneuvering, stability, and controlling the boat's heading.

Key Aspects of a Rudder:
Location: Usually mounted on the transom (back) or underneath the stern.

Mechanism: It pivots, acting as a lift-generating foil that directs water to change the boat's direction.

Types: Common types include spade (supported only from top), skeg-hung (attached to a protective fin), and transom-hung.

Operation: When the tiller is moved, the rudder redirects water, forcing the stern in the opposite direction, which pivots the bow toward the desired course.

Maintenance: Needs regular inspection for corrosion, damage to the rudder stock (the post it rotates on), and structural integrity.