Battlement

A battlement, in defensive architecture such as city walls and castles, is a parapet—a low protective wall between chest and head height—in which regularly spaced gaps or indentations, usually rectangular, allow defenders to launch arrows or other projectiles while the solid sections afford cover. The gaps are called embrasures, also termed crenels or crenelles; a wall or building furnished with them is described as crenellated, while the older synonyms castellated and embattled remain in common use. The act of cutting crenels into a previously unbroken parapet is known as crenellation.

The solid sections between crenels are called merlons. Battlements on walls protect a walkway, the chemin de ronde, running behind them; on towers or buildings the roof itself typically serves as a sheltered fighting platform.

A building might be designed from the outset with battlements, or an existing structure—a manor house, for example—might later be fortified by adding them. From the later Middle Ages onwards, battlements also became a widely used decorative motif on churches, secular buildings, and architectural details with no defensive function.