loo scannon

A small heavy apparatus on wheels with a short iron projectile-hurling barrel that you pack with black powder and a sandbag, and place just inside the door of an outhouse; you rig the device's primer-cap to both the door and the seat of the crapper. That way, if some "loose cannon" --- either because he's a pervert or simply too drunk to notice da "occupied" sign --- tries to enter da loo while someone else is already in there, he'll get blasted clear across the yard for his impudence.