Wrenches are tools that are used to tighten nuts, bolts, and anything else that needs to be turned. Wrenches are called spanners in British English. The first patent for a wrench was issued to Solymon Merrick in 1835. Since then, a large number of hand wrench types have been developed.

Wrenches are available in English and metric sizes. Products made in the United States are made to English system measurements, and products made elsewhere are made to metric system measurements. Consequently, workshops need both English and metric system sizes. Using the correct size of wrench is important to avoid harming the wrench and nut. To avoid harming user if dropped, wrenches should be pulled and not pushed.

The adjustable pipe wrench is used when the right size wrench is not available. Adjustable wrenches are made in two styles: locking and non-locking. Locking adjustable wrenches are generally better. Open-end wrenches have heads that are closed on two sides with one side open. They are used when the nut is not accessible to a box wrench.

Box wrenches have heads that are completely enclosed and provide more leverage than open-end wrenches. They are available in 6 point and 12 point versions to match the number of sides that the nut or bolt has. Combination wrenches have a box wrench and box spanner on one side and open-end wrench on the opposite. Both ends of the same wrench are generally the same size. Pipe wrenches have jaws that bite into the surface of the pipe and hold it for turning.

Aluminum pipe wrenches are popular due to their light weight, but they are more expensive, like the 24 pipe wrench. Allen wrenches, also called Allen keys and hex keys, are used with Allen screws. Allen wrenches can be either L shaped or T shaped. Socket wrenches fit over the nut or bolt head which makes removal easier than with other wrenches. Ratchet wrenches, which allow the socket to be turned by simply moving the handle backward and forward, are a common type of socket wrenches. Torque wrenches, a type of socket wrench, are used to apply a specific torque to a nut or bolt.