What is a monkey wrench?

A monkey wrench is a widely used tool that can be used to hold any number of materials in place. Invented in the 19th century, the first monkey wrenches were made from flat pieces of iron and measured 24 inches (61 centimeters) long. A monkey wrench has been described as having both an L- and F-shaped appearance. Basically, the monkey wrench has a fixed upper jaw with a lower jaw that can move up and down the wrench through a screw mechanism. It got the name "monkey wrench" because the movement of the lower jaw up and down the wrench seemed to look like a monkey climbing up and down a branch.

Once the monkey wrench was invented, a variety of modified wrenches and tools based on its basic design were also developed. Specialized wrenches, such as pipe wrenches, adjustable clamps and vice grips are all based on the standard monkey wrench, but they are designed to use in specific circumstances that can’t be handled by a monkey wrench.


The monkey wrench can be used to clamp onto pipes and various fasteners such as lug nuts, bolts and screws. The jaws of the monkey wrench are attached to the fastener head: This is where you want to slide the lower jaw to fit the specific fastener with a strong grip. Once both jaws of the monkey wrench firmly grip the flat sides of the fastener, you can begin to apply pressure to either tighten or loosen the fastener. If you want to tighten the fastener, turn the monkey wrench clockwise. Conversely, if you want to loosen a fastener, turn the monkey wrench counterclockwise.