What is the term for the kind of wrench that has a closed end and is used to tighten or loosen nuts or bolts?

The term for the kind of wrench that is specifically designed with a closed end to fit over nuts or bolts is known as a box-end wrench. This design allows for better grip and torque application as it encases the fastener completely, which minimizes the risk of rounding off the corners of the fastener head. Box-end wrenches often come in various sizes to match the hex shapes of different fasteners, making them ideal for tasks where maximum grip is required.

In contrast, a monkey wrench features an adjustable jaw that is useful for gripping and turning objects of different sizes, including pipes, but it does not have a closed end like a box-end wrench. A spanner wrench is typically associated with securing or loosening nuts found on items such as faucets or machine parts, and its design is not specifically closed-ended. Lastly, a pipe wrench is specifically designed for gripping round objects like pipes and is not suitable for use on nuts or bolts due to its design and function. Thus, the box-end wrench is the most accurate term for the described tool.