The challenge: To tie a knot in a piece of string that is being held at both ends without letting go of either end.
The secret: Lay the string or cord on a table. Then simply fold your arms, one above the other, right hand on upper left arm, left hand under upper right arm. With your arms thus folded, grasp one end of the string in each hand. Simply pull hands towards each other while maintaining your grasp on the string, and by the time your hands are separated, there will be a knot in the string.
