An adjustable wrench is a type of wrench with an adjustable jaw, which allows it to fit onto a range of different sized nuts and bolts. It is also commonly referred to as a crescent wrench or a shifting spanner.
The adjustable jaw is usually attached to a worm gear, which is turned by a thumbwheel or lever located at the base of the wrench. This adjusts the distance between the jaws, allowing the wrench to fit onto different sized fasteners.
Adjustable wrenches are useful in situations where a range of sizes of nuts and bolts need to be tightened or loosened, as only one tool is needed instead of multiple size-specific wrenches. However, they should not be used for high-torque applications, as they may slip and damage the fastener or cause injury to the user. For these types of applications, a torque wrench or a fixed-size wrench is recommended.