These Leg Irons use a classical screw and plug lock identical to the Froggatt Plug-8 Handcuffs. The back end of the key has two prongs that fit the plug to allow it to be screwed out. Once out, the key is screwed in clock-wise till it gets past the threading in the lock cylinder and then is inserted into the bolt and turned in opposite direction to unscrew it and allow the iron to open. The key is then screwed out and the plug screwed back in. The same operation, except for the direction of turning the bolt, is performed to lock them.