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

The tool used to tighten the set screw at the base of the drill stop is an Allen wrench, which is also known as a hex key. This tool is specifically designed for driving screws and bolts that have hexagonal (six-sided) indentations in their heads. Allen wrenches fit snugly into these recessed areas, allowing for a secure grip that enables the user to apply adequate torque when tightening or loosening fasteners.

In the context of drill stops, the set screw typically features a hex-shaped socket that requires an Allen wrench for effective operation. The design of the Allen wrench ensures that it can fit into tight spaces where other tools might not have adequate access, making it particularly suitable for adjustments on machinery or fixtures like drill stops. The hexagonal shape allows for efficient torque transfer, reducing the likelihood of slipping, which can occur with traditional screwdrivers or wrenches that do not match the fastener's shape.

This specific functionality and design make the Allen wrench the ideal choice for this task, ensuring that the set screw is secured firmly to maintain the integrity and proper functioning of the drill stop.