Battlement A battlement in defensive architecture , such as that of city wall s or castle s , comprises a parapet ( i . e . a defensive low wall between chest - height and head - height ) , in which rectangular gaps or indentations occur at intervals to allow for the discharge of arrows or other missiles from within the defences . These gaps are termed " crenels " ( also known as " carnels " , " embrasures " , or " wheelers " ) , and 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 merlon s ( 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 . Etymology . The term originated in about the 14th century from the Old French word " " , " to fortify with " batailles " " ( fixed or movable turrets of defence ) . The word " crenel " derives from the ancient French " cren " ( modern French " cran " ) , meaning a notch , mortice or other gap cut out often to receive another element or fixing . The modern French word for crenel is " creneau " , also used to describe a gap of any kind , for example a parking space at the side of the road between two cars , interval between groups of marching troops or a timeslot in a broadcast . Licence to crenellate . In mediaeval England a licence to crenellate granted the holder permission to fortify their property . Such licences were granted by the king , and by the rulers of the counties palatine within their jurisdictions , i . e . by the Bishops of Durham and the Earls of Chester and after 1351 by the Dukes of Lancaster . The castles in England vastly outnumber the licences to crenellate . Royal pardons were obtainable , on the payment of an arbitrarily determined fine , by a person who had fortified without licence . The surviving records of such licences , generally issued by letters patent , provide valuable evidence for the dating of ancient buildings . A list of licences issued by the English Crown between the 12th and 16th centuries was compiled by Turner & Parker and expanded and corrected by Philip Davis and published in " The Castle Studies Group Journal " . There has been academic debate over the purpose of licencing . The view of military - focussed historians is that licencing restricted the number of fortifications that could be used against a royal army . The modern view , proposed notably by Charles Coulson , is that battlements became an architectural status - symbol much sought after by the socially ambitious , in Coulson ' s words : " Licences to crenellate were mainly symbolic representations of lordly status : castellation was the architectural expression of noble rank " . They indicated to the observer that the grantee had obtained " royal recognition , acknowledgment and compliment " . They could however provide a basic deterrent against wandering bands of thieves , and it is suggested that the function of battlements was comparable to the modern practice of householders fitting highly visible CC - TV and burglar alarms , often merely dummies . The crown usually did not charge for the granting of such licences , but occasionally charged a fee of about half a mark . Machicolations . Battlements may be stepped - out to overhang the wall below , and may have openings at their bases between the supporting corbel s , through which stones or burning objects could be dropped onto attackers or besiegers ; these are known as machicolation s . History . Battlements have been used for thousands of years ; the earliest known example is in the palace at Medinet - Abu at Thebes in Egypt , which allegedly derives from Syrian fortresses . Battlements were used in the walls surrounding Assyrian towns , as shown on " bas relief s " from Nimrud and elsewhere . Traces of them remain at Mycenae in Greece , and some ancient Greek vases suggest the existence of battlements . The Great Wall of China has battlements . Development . In the European battlements of the Middle Ages the crenel comprised one - third of the width of the merlon : the latter , in addition , could be provided with arrow - loops of various shapes ( from simply round to cruciform ) , depending on the weapon being utilized . Late merlons permitted fire from the first firearm s . From the 13th century , the merlons could be connected with wooden shutters that provided added protection when closed . The shutters were designed to be opened to allow shooters to fire against the attackers , and closed during reloading . Ancient Rome . The Roman s used low wooden pinnacles for their first " aggeres " ( terreplains ) . In the battlements of Pompeii , additional protection derived from small internal buttresses or spur walls , against which the defender might stand so as to gain complete protection on one side . Italy . Loop - holes were frequent in Italian battlements , where the merlon has much greater height and a distinctive cap . Italian military architects used the so - called Ghibelline or " swallowtail " battlement , with V - shaped notches in the tops of the merlon , giving a horn - like effect . This would allow the defender to be protected whilst shooting standing fully upright . The normal rectangular merlons were later nicknamed Guelph . Middle East and Africa . In Muslim and African fortifications , the merlons often were rounded . The battlements of the Arabs had a more decorative and varied character , and were continued from the 13th century onwards not so much for defensive purposes as for a crowning feature to the walls . They serve a function similar to the cresting found in the Spanish Renaissance . Decorative element . European architects persistently used battlements as a purely decorative feature throughout the Decorated and Perpendicular periods of Gothic architecture . They not only occur on parapets but on the transom s of windows and on the tie - beams of roofs and on screens , and even on Tudor chimney - pots . A further decorative treatment appears in the elaborate paneling of the merlons and that portion of the parapet walls rising above the cornice , by the introduction of quatrefoil s and other conventional forms filled with foliage and shield .