What is the term for a wrench that completely encircles the bolt head?

The term for a wrench that completely encircles the bolt head is the box end. A box end wrench features a closed loop that fits over the hexagonal shape of a bolt head, providing a tight grip that minimizes the risk of rounding off the bolt. This design allows for effective torque application, especially in confined spaces where a traditional open-end wrench might not fit properly or provide enough grip.

Box end wrenches often come in various sizes to fit different bolt heads and can be used in conjunction with a ratchet for quick turn applications. This makes them particularly useful for tasks that require more torque and support, such as automotive repairs, where precision and grip are essential.