Abstract: A flexible curtain rollup door includes a drum mounted on a door frame and drivenly connected to an electric right angle gear motor unit. The frame includes opposed channel shaped guide tracks for receiving opposed side edges of a door curtain. Spaced apart elastically deflectable combination curtain stiffening struts and windlock members are secured to the curtain and include opposed windlock parts receivable in the guide tracks and configured, respectively, to provide for releasing only one side edge of the curtain from its guide track. A flexible transverse bottom bar includes plural side by side flexible bags filled with particulate material, secured to the curtain bottom edge and enclosed by a flexible envelope member. The curtain bottom edge includes a stiffener formed of interconnected links.