A modification of my previous handcuff blend, eliminating the chain concern I had.
Now, not only do the racheting bits rotate properly, but the whole thing moves properly, controlled by 3 empties:
A root control, for setting world rotation (and location).
An empty that controls each cuff, limiting its rotation to the axis of the hinge, with one empty following the other at the proper distance.
The hinges will always connect the two cuffs.
The only thing you can do that's not right is you can rotate them so they intersect, but other than that, everything works properly.
Thanks! I mostly do toonstyle renders and play with colors in the compositor, so I didn't need and probably couldn't produce a good material for it. I just needed cuffs, and Blendswap was experiencing a dearth of them.
Would be great with a metallic material.