Bolt rope

A bolt rope (Variants: "bolt-rope" and "boltrope", French: "ralingue", Spanish: "relinga", Old Norse: *"rár-línk", comprising "rár" genitive of "rá" "rope" and "línk" "edge of a sail "), is the rope that is sewn at the edges of the sail to reinforce them, or to fix the sail into a groove in the boom or in the mast.
Fore-and-aft sails often have bolt ropes on the leading edge (luff) where they attach to the mast and the bottom edge (foot) where they attach to the boom, which provide the terms, "luff bolt rope" and "foot bolt rope". They also occur on the edges of sails suspended from a spar, such as for gaff, square and lateen rigs.
Attachment and characteristics.
Bolt ropes were described as early as 1847, when Robert Kipping addressed "bolt-rope" attachment for a variety of sails, using sewing techniques appropriate to each, in his book, "The Elements of Sailmaking". He addressed the tradeoff between stiffness and flexibility to provide reinforcement without distorting the intended shape of the sail. He emphasized the need for the bolt rope not to affect the degree of slack on the leech (trailing edge) of a sail. He further emphasized that the rope must retain its original twist, as it is sewn in place, to avoid distorting the edge of the sail. He observed that, "Many a well-cut sail is spoiled by the roping."