A parapet is a barrier that is an upward extension of a wall at the edge of a roof,[1] terrace, balcony, walkway or other structure. The word comes ultimately from the Italian parapetto (parare 'to cover/defend' and petto 'chest/breast'). Where extending above a roof, a parapet may simply be the portion of an exterior wall that continues above the edge line of the roof surface, or may be a continuation of a vertical feature beneath the roof such as a fire wall or party wall.[2] Parapets were originally used to defend buildings from military attack, but today they are primarily used as guard rails, to conceal rooftop equipment, reduce wind loads on the roof,[3] and to prevent the spread of fires.