A monkey wrench is a type of adjustable wrench, usually quite large, used to turn fasteners such as bolts and nuts. Its design consists of an integral flat jaw, which can be adjusted to a specific size, allowing the wrench to securely grip a range of different-sized fasteners. The jaw can be easily adjusted through the use of a knurled adjustment wheel, and the length of the wrench can be adjusted using screws.
The unique shape of a monkey wrench provides the user with a secure grip and allows for more leverage than a standard adjustable wrench.