A great visual trick with the added benefit that the rope can be handed out before and after the performance!
You display a length of rope, and hand it out to your audience for inspection. Once it is returned, place the rope around your back, bringing an end around in each hand to the front. On the count of three, very quickly pull the ends of the rope. You will seemingly pull it right through your waist! The rope can now be handed out for inspection once again.