a slotted headstay system that contains two luff grooves to accommodate and provide continuous support for jibs or genoas that use boltrope. Usually made from aerodynamically shaped extruded aluminum or plastic and fitted over the headstay or forestay. A headsail is secured at the luff by sliding its luff tape/boltrope through a pre-feeder and then into the head foil feeder and up a groove. A dual-groove head foil allows for hoisting a second headsail in the second groove before dousing the first, so a boat can avoid running bare headed and losing performance. Harken’s brand is called Carbo Racing Foil. Schaefer Marine’s brand name is Tuff Luff. See also: jib peel.