Sheers. The elemental form of a pair of sheers consists in two spars fastened together near the top with a pulley at the point of junction, and held by a rope fastened to any convenient object, in such a position that the weight lifted hangs nearly between the spars. This forms an easily improvised crane. An apparatus of this kind of great height and strength is used for masting vessels. In the principal dockyards there are tall permanent sheers, mounted either on the side of a masting-dock or on a floating sheer-hulk, often an old dismantled ship devoted to this use.