The rules are simple. Find an unsuspecting target and use your open hand to smack the target's testicles with the knuckles in a flicking motion. One point is awarded for each testicle that is amputated from your target.
"It's just gotten way out of control," said Dr. Scott Wheeler, a urologist in Brainerd, Minn. who says he performs three to four surgeries a year on boys with ruptured testicles and other complications as a result of "sack tapping."
"All parents, you need to have this talk with your kids not to do it. It's lost its humor. It's not a game anymore. People get hurt," he added.