back flap
Isaac Kremer/ September 9, 2018/ / 0 comments
In a folding shutter, door, or the like, composed of two or more parts hinged together, that one which comes behind the others and next to the jamb when the shutter is open and folded back at the sides of the opening. Usually, the back flap is the one nearest the middle when the shutter is closed across the opening. (Sturgis, 1900)