What tool is commonly used to tighten or loosen bolts and nuts?

The tool commonly used to tighten or loosen bolts and nuts is a wrench. Wrenches are designed specifically for gripping and turning nuts and bolts, allowing for the application of torque, which is necessary to achieve the desired tightness or looseness. Different types of wrenches, such as open-end, box-end, and adjustable wrenches, provide versatility for various sizes and shapes of fasteners.

While other tools like screwdrivers and pliers can be used for different applications, they do not provide the grip or leverage needed for effectively working with bolts and nuts. A screwdriver is primarily designed for turning screws, and pliers, while capable of gripping objects, do not offer the same level of precision or torque control as a wrench. A hammer is used for striking and driving objects but is not intended for fastening or loosening bolts or nuts. Thus, the unique design and functionality of a wrench make it the appropriate tool for this task.