What tool is used to tighten the set screw at the base of the drill stop?

The correct tool to tighten the set screw at the base of the drill stop is an Allen wrench. Set screws typically have hexagonal sockets that specifically require the use of an Allen wrench, which is designed to fit into these hex-shaped recesses securely. This tool allows for greater torque application and control, making it easier to tighten or loosen the screw without risking damage to the screw head or surrounding components.

Using a flathead or Phillips screwdriver would not work effectively as they are designed for slotted and cross-headed screws, respectively, and would not fit the hex socket of a set screw. Similarly, while pliers can be used for various gripping and twisting tasks, they do not provide the precision needed to properly tighten a set screw, which could lead to the screw being improperly secured or even stripped. Hence, the Allen wrench is the ideal tool for this specific task, highlighting its importance in ensuring proper assembly and maintenance in aerospace applications.