You start off with a tennis ball and throw the ball continuously back and forth until somebody drops the ball. When someone drops the ball you say "Down on one knee". That person has to drop to one knee. Then the ball is thrown back and forth again and let's say the same person drops it a second time. Then you say "Down on two knees". If the same person drops the ball again you say "Down on one elbow", "Down on two elbows" and finally "Down on your chin." If you drop it after that you are out. But remember - you have to stay in the position you're in to catch and throw the ball.