Which of the following is commonly used for turning fasteners with hex heads?

The box end wrench is specifically designed to grip and turn fasteners with hex heads effectively. Its unique design features a rounded, enclosed end that fits over the fastener, providing a more secure grip compared to other tools. This design allows for equal distribution of force, which minimizes the risk of rounding off the corners of the fastener while turning. Additionally, the enclosed nature of the box end allows for working in tighter spaces where a straight tool might not fit, making it a versatile option for both mechanics and DIY enthusiasts.

In contrast, while pliers can be used for gripping various shapes, they are not ideally suited for hex heads as they do not provide the same level of grip and can easily slip, causing damage to the fastener. The open end wrench, while also capable of turning hex fasteners, offers less surface contact and grip compared to a box end wrench. Lastly, a screwdriver is designed primarily for turning slotted or Phillips head fasteners and is not an appropriate choice for hex heads at all.