The foot is the bottom, usually horizontal edge of a sailboat's sail, extending between the forward tack and rear clew. On a mainsail, it typically attaches to the top of the boom, though it may be "loose-footed" (unattached). It controls the lower shape of the sail and is often tensioned using an outhaul.

Key Features of the Foot:
Location: The lower edge connecting the tack (front corner) to the clew (back corner).

Attachment: On most modern boats, the foot is attached to the boom.

Function: Along with the leech and luff, it defines the sail's shape and efficiency.

Controls: The outhaul line connects to the clew to tension the foot, flattening the sail in high winds or loosening it for power in light winds.

Loose-footed: A sail that does not attach to a boom along its foot is called "loose-footed".