纵帆滑车, 三倍复滑车

Luff \Luff\ (l[u^]f), n. [OE. lof, prob. a sort of timber by
which the course of a ship was directed, perh. a sort of
paddle; cf. D. loef luff, loeven to luff. The word is perh.
akin to E. glove. Cf. {Aloof}.] (Naut.)
(a) The side of a ship toward the wind.
(b) The act of sailing a ship close to the wind.
(c) The roundest part of a ship's bow.
(d) The forward or weather leech of a sail, especially of
the jib, spanker, and other fore-and-aft sails.

{Luff tackle}, a purchase composed of a double and single
block and fall, used for various purposes. --Totten.

{Luff upon luff}, a luff tackle attached to the fall of
another luff tackle. --R. H. Dana, Jr.