Yazzo Keyed Swivel Mount

I need swivels that can quickly be attached to other things that have the matching notch in them.

This thing has a key that fits into a notch, like the notches on this thing: http://www.thingiverse.com/thing:5874

What would you do with it? Attach this thing to something else. Then put a 5/16" (M8) rod through the holes. It can swivel freely, so you've just made an easy mounting axle. Now attach interesting other things to the axle, and there you go!

This thing has some mounting ho