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"Curtain, in Fortification, is the portion of rampart or wall between two bastions or two gates. In a regular siege, to batter down the curtain is one of the main operations depended on; and many of the external works constructed by the defenders are intended to frustrate, or at least embarrass, this operation. In the annexed cut, which shows a ground-plan of some of the elements of a regular fortification, FF' is the curtain; HAEF, a bastion. The component parts of the bastion are thus designated: AH and AE, two faces; EF and GH, two flanks; A, the salient; FG, the gorge; and H and E, the shoulders. mn is the rampart; mo, the parapet on the rampart; QPQ', the ditch; NO, the covery-way; RWR', the glacis; KLL', a ravelin." — Chambers' Encyclopedia, 1875

Curtain

"Curtain, in Fortification, is the portion of rampart or wall between two bastions or two gates. In…