Two sticks held together in the same hand; each one has a tassel attached to a thin rope. Pull downward on one of them and the other one will go up, or vice-versa. Repeat this more than once and your audience will think that the two sticks are somehow joined together. But, even if you move the two ends of the sticks away from each other, the ropes will keep on interacting and moving up and down. (age 7 +)
