What tool is used for holding a bolt tap?

The tap wrench is specifically designed to hold and turn taps, which are tools used for cutting threads on the inside of holes to create a screw thread. The design of a tap wrench allows it to grip the square end of the tap securely, enabling the user to apply the necessary torque to properly thread a hole without damaging the tap or the workpiece. This makes it an essential tool in machining and metalworking where precision and clean threads are critical for proper assembly.

While the other tools mentioned can be useful in various mechanical applications, they do not serve the same specialized purpose as a tap wrench. For instance, an adjustable wrench is versatile for gripping and turning various sizes of nuts and bolts but lacks the precision required for taps. A socket wrench is also useful for turning fasteners but is configured for external threads rather than internal ones. Pliers can grip and twist objects but would not provide the necessary control and alignment needed for tapping threads. Thus, the tap wrench stands out as the correct tool for the task of holding a bolt tap.