Abstract: Modular, selectively employable building parapet roof-rim structure including (a) gravity-docking reception structure deployed along and adjacent at least a portion of the perimeter of a building roof structure which is adjacent the top of a building frame, and (b) a dockable, modular parapet unit including gravity-docking structure removably and replaceably dockable, under the influence of gravity, with the reception structure to dispose the parapet unit as at least a part of an outwardly visible parapet roof-rim structure associated with the building roof structure. The parapet structure may be associated with moisture-barriering flashing structure which becomes locked into place along the rim of a building roof between inter-engaging components in the parapet structure.