Using your hand like the GI Joe Kung Fu grip, you grab the inside of a person's leg, near their genitals.
Usually squeezing as hard as possible for for at least 10 seconds.
The goal being pain and making sure the inside of their thigh bruises badly.
My leg is killing me, I was at the ballet last night and a stripper gave me a crowbar hold when I told her I didn't want a 6th dance.