[other traps]

Handcuffs Puzzle Box

This is one of my early attempts at a puzzle box where the goal is to get it open at all (rather than just get it open without going boom), and it was mostly an experiment in adapting existing disentanglement puzzles for puzzle boxes. It's based on one of the simplest disentaglement puzzles I know — it's called "The Two Captives" in Joseph Leeming's 1940 book Fun With String, but the basic workings is undoubtably much older.

The box is kept shut by two chains, one attached to a sliding rod on the lid and the other to an identical rod on the box side. Each chain is connected to its respective rod via two loose rings that act as shackles, with end caps to prevent the rings from being removed, and the two chains are looped around eachother to keep the box closed.

Solution

Thread the middle of one of the chains through one of the rings on the opposite side (turning the eye bolt and/or sliding the rod to make enough slack if necessary). Then bring the loop around the corresponding endcap and back through the ring again. At this point the chain can be brought back over the endcap again and the two chains will be free of each other.

Equipment

• Box with either hinged or a sliding lid. The box should be designed so that opening it as far as the chain slack will allow won't allow access to the contents. (I did this by adding nails to the inside of the box, but that's an ugly hack.)
• Two T-shaped handles with larger end caps. These can be ornamental or made from a large eye bolt, a dowel that can fit through the eye, and two washers to prevent the dowel from sliding out.
• Two chains (or strings) that can be afixed to rings
• Four rings that fit freely over the "arms" of the handle but but not over the end caps. You should be able to attach the chain to the rings and fit the rings over the end caps in a way that cannot be easilly removed (e.g. by soldering the chain afterwards or gluing on the end caps).

Construction

1. Attach one handle to the frame of the box and the other to the lid
2. Thread rings onto each of the "arms" of the handles so they can't be removed over the end caps
3. Attach handles so that when the chains are entangled the box can't be opened
4. Attach rings to all four chain ends so they work like shackles
5. Entangle the two chains by reversing the solution described above

Ideally you want the chains to have just enough slack to easilly solve the puzzle, which can be a little tricky to get right. I recommend using string or adjusting the chain to find the perfect length before cutting and permanently attaching them.

In my version the rods are threaded through eye bolts that allow them to both slide and freely rotate, but if I were doing it again I'd make them stationary and just add enough slack to the chains to solve the puzzle — I feel like the extra degrees of freedom doesn't really add anything to the puzzle. I'd also replace the hinged-lid box with a sliding-lid kind, and add a lip under the lid so it can't be opened even a little bit without disentangling the chains.