Jib

A jib is the triangular headsail set forward of the mast on the forestay of a fore-and-aft rig. It accelerates and redirects the airflow over the lee side of the mainsail, so the two sails together drive the boat far better upwind than either alone. A working jib is cut inside the foretriangle; when the headsail overlaps the mast it becomes a genoa. The jib is hoisted on a halyard and trimmed with sheets led to the cockpit.