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

The use of an Allen wrench to tighten the set screw at the base of the drill stop is the most suitable option. An Allen wrench, which is also known as a hex key, is specifically designed to fit into hexagonal socket screws. These screws, which often have a recessed hexagon-shaped hole, require a tool that can fit perfectly within that shape to apply adequate torque without stripping the screw.

In the context of aerospace assembly, where precision and control are paramount, using the correct tool is essential. Allen wrenches allow for a more secure grip on the screw, ensuring that it is tightened effectively without risking damage or slippage.

Tools like socket wrenches, open-end wrenches, and adjustable wrenches are typically used for different types of fasteners, such as nuts and bolts with external heads, but they would not provide the same fit and effectiveness for a hex socket screw. This reinforces why the Allen wrench is the correct choice for this application.