The lower edge of a triangular sail is called the foot of the sail, while the upper point is known as the head. The halyard, a line which raises the sail, is attached to the head. The lower two points of the sail, on either end of the foot, are called the tack (forward) and clew (aft). The tack is shackled to a fixed point on the boat such as the gooseneck in the case of a mainsail or the deck at the base of a stay in the case of a jib or staysail. The clew is movable and is positioned with running rigging, an outhaul on the mainsail and a sheet for a headsail. A symmetrical sail may be said to have two clews.

The foot of a sail is its lowest edge, bounded by the clew and the tack or on some sails by the two clews.

The forward edge of the sail is called the luff, which inspires the term luffing, a condition where the sail ripples because wind is crossing over the front and back side simultaneously. A cunningham may be rigged on the mainsail to control sail shape. The aft edge of a sail is called the leech.