A Scrotum Shell is generally seen as a very hard ball-sack. The most common reason for this is when a man (or woman) ejaculates upon the ball-sack, rubs it in, and leaves it to dry overnight. Upon inspection in the morning, the ball-sack should have a shiny, hard layer, although this depends on the constitution of the semen.
That girl was rubbing my scrotum shell all night
by PooMister November 15, 2010