Abstract: A roll-up closure device (FIG. 1) comprising a light weight flexible curtain (1), an extruded profiled edge (2), a synchronizing drive mechanism (3), a vertical retaining means (6) and a take up means (7). Said roll-up closure device eliminates the need for horizontal retaining mechanism positioned across the opening and the counter balance devices commonly associated with light weight flexible curtain roll-up closure devices as a means of preventing the curtain from being pulled out of the vertical retaining guides due to differential pressures that may exist in the closure device environment.