Metal Fiddle - We bought this years before we actually modified and used it (it was a bargain) so I cant exactly remember where we acquired it from, but I am glad we did. We modified it by drilling holes and gluing high strength neodymium magnets into the holes. This may seem obvious but magnets will have to be placed in the opposite side facing position (when closed). We found that machining and adding the magnets to one side at a time then clamp it together with a piece of paper between so the glue doesn't stick the sides together made a better working fiddle, also the magnets should be a press fit, not lose as they may sink below the surface and loose the magnetic holding force. As we are using magnets the fiddle material has to be non-magnetic, our fiddle is made of aluminium. Brute strength is required to open, maybe by a second person to pull it open, as opening is difficult by the prisoner as they don't have the leverage, but if you are worried they maybe able to escape then use more or longer / stronger magnets. Only small magnets are require for the wrist parts as they will be held firmly when the fiddle is closed. Below are a few pictures to give you an idea of where we added the magnets and a picture of Lucy Lauren trapped using the fiddle.