<P> A battlement in defensive architecture , such as that of city walls or castles , comprises a parapet ( i.e. , a defensive low wall between chest - height and head - height ) , in which gaps or indentations , which are often rectangular , occur at intervals to allow for the launch of arrows or other projectiles from within the defences . These gaps are termed `` crenels '' ( also known as carnels , embrasures , or wheelers ) , and the act of adding crenels to a previously unbroken parapet is termed crenellation . Thus , a defensive building might be designed and built with battlements , or a manor house might be fortified by adding battlements , where no parapet previously existed , or cutting crenellations into its existing parapet wall . The solid widths between the crenels are called merlons ( also cops or kneelers ) . A wall with battlements is said to be crenelated or embattled . Battlements on walls have protected walkways ( chemin de ronde ) behind them . On tower or building tops , the ( often flat ) roof is used as the protected fighting platform . </P>
<P> A battlement in defensive architecture , such as that of city walls or castles , comprises a parapet ( i.e. , a defensive low wall between chest - height and head - height ) , in which gaps or indentations , which are often rectangular , occur at intervals to allow for the launch of arrows or other projectiles from within the defences . These gaps are termed `` crenels '' ( also known as carnels , embrasures , or wheelers ) , and the act of adding crenels to a previously unbroken parapet is termed crenellation . Thus , a defensive building might be designed and built with battlements , or a manor house might be fortified by adding battlements , where no parapet previously existed , or cutting crenellations into its existing parapet wall . The solid widths between the crenels are called merlons ( also cops or kneelers ) . A wall with battlements is said to be crenelated or embattled . Battlements on walls have protected walkways ( chemin de ronde ) behind them . On tower or building tops , the ( often flat ) roof is used as the protected fighting platform . </P>
what are the up and down bits on a castle called
what are the up and down bits on a castle called
`` crenels ''
`` crenels ''