Ropecuffs.

I already mentioned, that it's a bad idea to use a pair of holiday handcuffs to suspend your partner from, and here's the rope cuffs the answer.
They can be made in different ways, and I'll show you two ways to do so.

We'll start out with the easy ones:

1/ Make a bow on a piece of rope, and place it on your partners arm.
Wind the long end of the rope around your partners arm 5-6 times.

2/ Pull the long end through the loop, and pull the short end carefully, until the long end is lying nicely, locked alongside the windings.

3/ End the cuff, by tying a reefers knot between the ends of the rope.

If you'd like to strain the cuff, it'll be an advantage if you lay the reefers knot on the palm side of the arm, as this will allow your partner to grip the rope.

For suspensions, I'll recommend the next cuff, which is a little more complicated, but much more effective for that. Next