Abstract: A door frame with a substantially continuous sealing surface supports a door with a substantially continuous sealing member mounted thereon. A stepped U-shaped frame member has an opening at one end that is closed with a square-cut member, such as a threshold. The frame, threshold and hinges mounted on the frame provide a substantially continuous sealing surface. The bores of the hinge knuckles may be matched with bushings in the bores, so that the bushings must be properly oriented. The heads of the bushings may have at least two steps or raised contact surfaces and at least two indentations or depressed contact surfaces. When the doors are opened, the steps on their bushings in the pivoting hinge leaves drop into the indentations in the adjacent fixed hinge leaf and hold the door in position.

Abstract: A door frame with a substantially continuous sealing surface supports a door with a substantially continuous sealing member mounted thereon. A stepped U-shapped frame member has an opening at one end that is closed with a square-cut member, such as a threshold. The frame, threshold and hinges mounted on the frame provide a substantially continuous sealing surface. The bores of the hinge knuckles may be matched with bushings in the bores, so that the bushings must be properly oriented. The heads of the bushings may have at least two steps or raised contact surfaces and at least two indentations or depressed contact surfaces. When the doors are opened, the steps on their bushings in the pivoting hinge leaves drop into the indentations in the adjacent fixed hinge leaf and hold the door in position.