A wrench is a commonly used installation and removal tool. It is a hand tool that uses the principle of leverage to turn bolts, screws, nuts and other threaded fastening bolts or nuts. Wrenches are usually made of carbon or alloy structural steel.

The wrench usually has openings or sleeve holes for holding the bolt or nut at one or both ends of the shank. When in use, an external force is applied to the shank in the direction of thread rotation to turn the bolt or nut.

There are basically two types of wrenches, dead wrenches and adjustable wrenches. The former refers to the wrench that has a fixed number written on it, and the latter is the adjustable wrench. 1. Dead wrench: One or both ends have an opening of a fixed size, which is used to twist a nut or bolt of a certain size. 2. Torx wrench: Both ends have working ends with hexagonal or twelve-sided holes, which are suitable for occasions where the working space is narrow and ordinary wrenches cannot be used. 3. Dual-purpose wrench: one end is the same as the single-span wrench, the other end is the same as the torx wrench, and the two ends are screwed with the same specification of bolts or nuts. 4. Adjustable wrench: The width of the opening can be adjusted within a certain size range, and it can turn bolts or nuts of different specifications. The structural feature of the wrench is that the fixed jaw is made of a flat jaw with fine teeth; one end of the movable jaw is made of a flat jaw; the other end is made of a concave jaw with fine teeth; The jaws can be quickly removed and the position of the jaws can be changed. 5. Hook wrench: Also known as crescent wrench, it is used to twist flat nuts with limited thickness. 6. Socket wrench: It is composed of multiple sockets with hexagonal holes or twelve-pointed holes and equipped with various accessories such as handles and connecting rods. It is especially suitable for screwing bolts with very narrow or deep depressions. or nuts. 7. Allen wrench: an L-shaped hexagonal bar wrench, specially used for turning the Allen screws. The model of the Allen wrench is based on the size of the opposite side of the hexagon, and the size of the bolt has national standards. Application: It is specially used for tightening or dismantling round nuts on machine tools, vehicles and mechanical equipment. 8. Torque wrench: it can display the applied torque when turning the bolt or nut; or when the applied torque reaches the specified value, it will emit light or sound signal. Torque wrenches are suitable for installations with clearly defined torque levels.