I feel like an idiot, but I can't figure out exactly how this torque angle gauge works.

When I turn it, everything turns (including the gauge), so it doesn't tell me how far I have turned.

It seems like the hex key looking thing must do something, but I don't know exactly what.

I would appreciate any advice on how to use this properly. Thanks.

Link to pic of my gauge:
http://www.greatnecksaw.com/images/p...dium/25424.jpg