A mythical structure that would have been placed in the backyard of the user. There would be minimal amenities inside of it; electricity, heating, cooling, seats, a table - nothing too fancy. The sides of the building, however, would have holes drilled into it so paid workers could blow "shotties" through the holes, thus helping the occupants to get "hotboxed" inside the building.
The building could also be used to have sex with girls when no other location is available. (See "Shack 'Er")
"We are meeting up at The Shack to smoke a bag, you coming?"