jackstay

A stay for racing or cruising vessels used to steady the mast against the strain of the gaff.

A rope, rod, or batten along the upper side of a yard, gaff, or boom to which a sail is fastened.

A rope or rod running vertically on the forward side of the mast on which the yard moves.

Nautical: One of a set of ropes, iron rods, or strips of wood attached to a yard or gaff for bending a square sail to.

A rod or rope running up and down on the forward side of a mast, on which the square-sail yard travels; a traveler.

A rail of wood or iron stretching along a yard of a vessel, to which the sails are fastened.

A stay (rope, bar or batten), running along a ship’s yard, to which is attached the head of a square sail.