Put a rubber band on the fingers of each hand, as shown. Move the rubber bands back and forth, demonstrating that they are joined to each other. Then stretch them out, and suddenly they become separated!
The secret of the magic trick is that you switch fingers when stretching out the rubber bands, as shown.
However, you must hide what you are doing from your audience, using your other fingers. Make the switch quickly, and your audience won’t guess what has happened!