I bought one for school last year and have yet to use it (asides from the pica ruler) or receive adequate instruction on how to use it. A few of my type teachers have mentioned how they are handy, and everyone should have one, but no one has shown why.

I even went to the Library last week and was looking at Graphic Design studio technique books, and while they mentioned more about it's uses, I think it was assumed that their pre-macintosh readers already knew how to use them.
And now that I'm taking an editorial class, I'd like to actually use one with confidence.

So I humbly ask two questions, how exactly do you use a type gauge, and as a professional do you still use one?

thanks one million
Mike