What tool is used to turn nuts and bolts, often with adjustable jaws?

Wrenches are specifically designed tools used for gripping, fastening, turning, or loosening nuts and bolts. The key feature of a wrench is its adjustable jaws in some designs, like an adjustable or crescent wrench, which allow it to accommodate various sizes of nuts and bolts. This adaptability makes wrenches essential in mechanical work, maintenance, and assembly tasks, where different fastener sizes are commonly encountered.

In contrast, a hammer is primarily used for driving nails or breaking apart objects, and lacks the necessary grip for turning fasteners. A screwdriver is intended for driving screws, which have a different shape and function compared to nuts and bolts, and thus is not effective for that purpose. Lastly, a mallet is often used for striking without damaging the work surface, but it does not possess any gripping or turning capability. Therefore, wrenches stand out as the appropriate choice for turning nuts and bolts.