n. 起重三角架, 人字起重架

Shears \Shears\, n. pl. [Formerly used also in the singular. See
{Shear}, n., 1.]
1. A cutting instrument. Specifically:
(a) An instrument consisting of two blades, commonly with
bevel edges, connected by a pivot, and working on both
sides of the material to be cut, -- used for cutting
cloth and other substances.

Fate urged the shears, and cut the sylph in
twain. --Pope.
(b) A similar instrument the blades of which are
extensions of a curved spring, -- used for shearing
sheep or skins.
(c) A shearing machine; a blade, or a set of blades,
working against a resisting edge.

2. Anything in the form of shears. Specifically:
(a) A pair of wings. [Obs.] --Spenser.
(b) An apparatus for raising heavy weights, and especially
for stepping and unstepping the lower masts of ships.
It consists of two or more spars or pieces of timber,
fastened together near the top, steadied by a guy or
guys, and furnished with the necessary tackle.
[Written also {sheers}.]

3. (Mach.) The bedpiece of a machine tool, upon which a table
or slide rest is secured; as, the shears of a lathe or
planer. See Illust. under {Lathe}.

{Rotary shears}. See under {Rotary}.