Luff

The leading edge of a sail.

How to sign

Use Dominant 1-hand, fingers together: edge line. The base or passive hand is Non-dominant flat-B: sail plane. Set the sail plane. Put the index at the tack/low forward corner. Trace upward along the forward edge nearest the mast or forestay. Hold at the head/top corner as the luff endpoint. Establish a sail triangle. With a 1-hand, trace its forward edge from tack upward to head. Keep the line nearest mast or forestay.