Effect:

A ring is locked on a spring. A spectator is asked to remove the ring from the spring, but cannot do so.

Secret:

To remove the ring, bring it to the center of the spring. Now twist the ring against the two wires on the spring so the ring turns 180 degrees in the opposite direction past the wires on the spring. You can lift the ring up and easily slide it up and off the spring.

To lock the ring back on the spring, simply place it over the middle of the spring and twist 180 degrees against the wires on the spring.