The slaughterhouse is a location in Lakeview Cabin IV.
The slaughterhouse is a large brown building to the left of the map. It has no windows and only 1 door. Above the door is the slaughterhouse logo (a pig) and it's name: Lakeside Slaughterhouse.
Once you enter, you have to choose between 2 doors. Both lead to a trap maze, where choosing a wrong door will drop your character into a saw room from wich they cannot escape. Upon completing the maze, they either reach Piggy's room or a room in the mansion.
The player has to visit the slaughterhouse and get the gas canister from Piggy's room in order to finish lakeview cabin IV (unless they get lucky and the gift room in the mansion contains gasoline). Taking the gas will wake up Piggy, who will chase you down the slaughterhouse. He ignores traps and always chooses the correct door, but doesnt open doors, sawing them down instead, giving you a waning he is about to enter the room.