Problem: You can see that Allen screw in the hole just below the surface, but can't tell what size wrench to use.

Problem: You can see that Allen screw in the hole just below the surface, but can’t tell what size wrench to use. Is there a way to determine the right tool without using the trial-and-error method?

Solution: Push your finger into the top of the setscrew. The impression made on the fingertip can then to matched to the proper wrench size.

Contributor: Tom Pivarnik, Substation Mechanic, PSE& G Co., Somerset, NJ