A murder hole or meurtrière is a hole in the ceiling

Ceiling

A ceiling is an overhead interior surface that covers the upper limit of a room. It is generally not a structural element, but a finished surface concealing the underside of the floor or roof structure above....

 of a gateway

Gate

A gate is a point of entry to a space enclosed by walls, or a moderately sized opening in a fence. Gates may prevent or control entry or exit, or they may be merely decorative. Other terms for gate include yett and port...

 or passageway in a fortification

Fortification

Fortifications are military constructions and buildings designed for defence in warfare and military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs...

 through which the defenders could fire, throw or pour harmful substances, such as rocks, arrows, scalding water, hot sand, quicklime

Calcium oxide

Calcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....

, tar, or boiling oil, down on attackers. They also allowed water to be poured onto fires started within the gate passage. Similar holes, called machicolation

Machicolation

A machicolation is a floor opening between the supporting corbels of a battlement, through which stones, or other objects, could be dropped on attackers at the base of a defensive wall. The design was developed in the Middle Ages when the Norman crusaders returned. A machicolated battlement...

s, were often located in the curtain walls

Curtain wall (fortification)

A curtain wall is a defensive wall between two bastions of a castle or fortress.In earlier designs of castle the curtain walls were often built to a considerable height and were fronted by a ditch or moat to make assault difficult....

 of castles

Castle

A castle is a type of fortified structure built in Europe and the Middle East during the Middle Ages by European nobility. Scholars debate the scope of the word castle, but usually consider it to be the private fortified residence of a lord or noble...

, fortified manor houses

Manor house

A manor house is a country house that historically formed the administrative centre of a manor, the lowest unit of territorial organisation in the feudal system in Europe. The term is applied to country houses that belonged to the gentry and other grand stately homes...

 and city walls. The parapet

Parapet

A parapet is a wall-like barrier at the edge of a roof, terrace, balcony or other structure. Where extending above a roof, it may simply be the portion of an exterior wall that continues above the line of the roof surface, or may be a continuation of a vertical feature beneath the roof such as a...

 would project over corbels

Corbel

In architecture a corbel is a piece of stone jutting out of a wall to carry any superincumbent weight. A piece of timber projecting in the same way was called a "tassel" or a "bragger". The technique of corbelling, where rows of corbels deeply keyed inside a wall support a projecting wall or...

 so that holes would be located over the exterior face of the wall, allowing the defenders to target attackers at the base of the wall.

See also

• Bretèche
  Bretèche
  In medieval fortresses, a bretèche or brattice is a small balcony with machicolations, usually built over a gate and sometimes in the corners of the fortress' wall, with the purpose of enabling defenders to shoot or throw objects at the attackers huddled under the wall. Depending on whether they...
  
  
• Machicolation
  Machicolation
  A machicolation is a floor opening between the supporting corbels of a battlement, through which stones, or other objects, could be dropped on attackers at the base of a defensive wall. The design was developed in the Middle Ages when the Norman crusaders returned. A machicolated battlement...
  
  
• Merlon
  Merlon
  In architecture, a merlon forms the solid part of an embattled parapet, sometimes pierced by embrasures. The space between two merlons is usually called a crenel, although those later designed and used for cannons were called embrasures.-Etymology:...
  
  
• Hoarding
  Hoarding (castles)
  A hoarding was a temporary wooden construction that was placed on the exterior of the ramparts of a castle during a siege.The purpose of a hoarding was to allow the defenders to improve their field of fire along the length of a wall and, most particularly, directly downwards to the wall base.The...