You will think Houdini is alive again with this one! The magician borrows a string/rope and a key ring or some such circular object. He then folds the rope in half and threads the folded part through the ring, next placing the free ends through the loop, thus encapsulating the ring on one end. Next, while the magician holds the end with the ring, the spec is asked to tie a knot in the other end. After doing so the rope is examined to make sure it is secure. Then the magician just rubs the ring and rope and the ring melts right off! Amazing!
You can do this with a shoelace and a key ring if you do not want to carry the objects with you. This way all the items can be borrowed.
This trick is suitable for all levels.