Here‘s a simple and highly effective trick which is quite mystifying when you do not know the secret.
Trick: A borrowed piece of string is knotted. It is now doubled and cut. The four ends are visible. The string is then restored to one piece and handed out for examination.
Secret: When you double the string, give it a half twist as in Illustration #1 so that after it is doubled it forms two interlocking loops as in Illustration #2. You hold your thumb and forefinger over the loops so that they are concealed. Now invite your child to cut the string about one-half inch from the loop. Four ends will now be visible However, only two ends are real, the other two being fake. Put the fake ends in your mouth and work the small piece off with your teeth. Now hand the restored string out for examination. At the first opportunity, get rid of the fake piece in your mouth.