battlement

Parapet (portion above the roof) of the exterior wall of a fortification, consisting of alternating low portions (crenels) and high portions (merlons). Rooftop defenders would shoot from behind the merlons during times of siege. Medieval battlements were often bracketed out (see corbel) to form a machicolation (overhang) with holes in its floor through which objects could be dropped on encroachers below.

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