A Ring Strangely Becomes Threaded on A Cord

Sometimes the magic in a display is not so much about the result, but the speed in which it was accomplished.
A cord is stretched between the magician's wrists, and tied securely to each one.
A ring is then introduced, and may be checked for authenticity by the audience. In the blink of an eye, the ring is seen threaded n the cord, dangling freely between his wrists. Both the cord and the ring can be removed and examined by the audience members.