"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Hex wrenches, also known as Allen keys, are the tools you use to screw and unscrew fasteners that have a ...

In this quick shop tip, I show how I stop guessing which hex key fits a tiny set screw on my machine. I remove the screw, bring it over to my tool rack, and test it on the Allen keys until I find the ...