The act by which a male participant grasps the undermost skin of the scrotum (directly above the foremost part of the taint) using only the second knuckles of every finger. Meanwhile, while utilizing both thumbs, push the head of the flaccid phallus into the scrotum itself. Creating the 'frightened turtle' illusion. With the fingers still clasped, simply pull the undercoating over the thumbs and release them. (Think of this as over-tucking into bed.) If all goes accordingly, you have just executed the Triple Sac and have become three times the man of Tom Green.
While trimming your marvelous ball fro, attempt to incorporate the triple sac method to prevent minor cuts, dings and razor burn to the undersack.