Which tool is primarily used for turning hex head nuts and bolts?

The box end wrench is specifically designed for engaging with hex head nuts and bolts. Its closed-loop design grips the fastener more securely than an open-end wrench, which minimizes the risk of slipping off the nut or bolt during application of torque. The interior shape of the box end is tailored to fit the contours of hexagonal fasteners, allowing for a snug fit that provides better leverage. This makes it particularly effective for applying torque required to tighten or loosen bolts and nuts without damaging their surfaces.

In contrast, a socket wrench relies on interchangeable sockets to fit various sizes of nuts and bolts but is not classified as a box end wrench, even though it serves a similar purpose. Pliers do not offer the same level of precision or grip for hex head fasteners, and an adjustable wrench, while versatile, can slip off hex nuts if not adjusted precisely, potentially damaging the fastener or the tool. Therefore, when focusing on turning hex head fasteners, the box end wrench clearly excels due to its tailored design and secure grip.