Common practice in sports where males are required to wear a cup all across the world. It involves a coach or player taking a sharp or heavy object and jabbing the unmentionable area with all one's might. If the subject is wearing a cup/jock strap, little or no pain will result. However, if the individual is not wearing what he's supposed to be wearing, severe agony and probable paralysis may occur. It's intended for the safety of the player, although the actual practice of the cup check seems the antithesis of safety.
Now, when someone's going around performing cup checks, what's the obvious thing to do if you're not wearing a cup? Either run away or tell the person about to slam you in the testicles you're not wearing a cup, even though the likely punishment in running your ass, of course. While running is bad, there is no comparison between running and getting smacked in the balls. However, a poor teammate of mine this year was not blessed with the gift of intelligence:
A cup check was coming. All of the players on the team were lined up at attention, with our crazy coaches bat in hand, slamming each player in the balls. This is why everyone on my team wears a cup. However, poor little Johnny, as we shall call him, had forgotten his cup. He stood there nervously, wiggling around, watching in dread as the insane coaches neared him with their bats of doom. Yet he never cried out or said anything. Three people away one coach came, then two, then one and BAM!
Everyone (coaches included) watched with a mixture of horror and comedy as Johnny cried out and fell to his knees, writhing on the ground in pain. After the coach performed his famous gay rape maneuver, Johnny appeared to be humiliated, but alright. As for his chances for procreation, well that's another story......