A sure fire laugh getter! An assistant from the audience is called upon to help you. Before they touch your props, they are asked to wipe their hands on a hand towel given to them.
The hand towel is casually shown to be clean on both sides. After the assistant wipes their hands the hand towel is covered with black hand prints!
This is guaranteed to get you a big laugh.
Trick hand towel may be used over and over again.