This is a pre-owned item.
The magician’s wrists are secured with a length of rope so as to leave a portion of rope between the hands. A solid metal ring, that can be examined, is handed to the performer, who turns around for just an instant. When he faces the audience again the ring is seen to be on the rope! Now the performer’s wrists are untied and both the rope and ring can be examined. They will find nothing wrong.
Very easy to do!