murder-hole

A murder-hole or meurtrière is a hole in the ceiling of a gateway or passageway in a fortification through which the defenders can fire, throw or pour dangerous or noxious substances at attackers. As a result, the defenders would be able to rain rocks, arrows, heated sand, boiling oil, water and incendiary devices, and other substances down on the attackers' heads. Similar holes, called machicolations, were often located in the curtain walls of castles, fortified manor houses and city walls. The parapet would project over corbels so that holes would be located over the exterior face of the wall, and arrows could be shot at, rocks dropped on, or boiling water poured over, any attackers near the wall.