Before the development of furling headsails, the headsail had to be hanked onto the forestay or the luff rope was fed up inside a foil. While hanked-on sails are still used on many boats, furling headsails are used on most cruising boats, especially midsize and larger boats.
At the base of the furling unit is the furling drum. Above it is the furling foil, a flexible grooved structure that surrounds the forestay from the drum to a swivel at the top of the stay. The jib is hoisted with its leading edge in the groove of the foil—typically only once at the beginning of the sailing season. Then the furling line is pulled out of the drum, causing the drum and foil to rotate and the sail to roll up around the foil.
With a furling headsail there is no need to lower it and remove the sail hanks after each sail. A furled headsail always remains raised and ready for use.