A plain or notched, often wedge-shaped piece of wood or metal designed to hold parts of a machine or structure in place or provide a bearing surface, usually adjusted by a screw or key.扁柱,夹条,凹字形楔一种平的或有凹的经常是一块楔形的木头或金属,用来在一定地方夹住机器或结构的各部分或提供轴承的表面,通常是由螺丝或钥匙来调整