Abstract: A retractable curtain-like closure for a vehicle such as a trailer includes an automatic retraction mechanism and vertical and horizontal tensioning mechanisms. Once the curtain has been extended over an open side of the vehicle, the curtain is vertically tensioned by rotation of a roll bar extending along a bottom edge of the curtain until the curtain is taut. The roll bar is held in position during vertical tensioning by a series of hooks located along a bottom edge of the trailer. The curtain is tensioned in a horizontal direction by connecting the side edges of the curtain to a rotatable rod by a series of pins and rotating the rod to tension the curtain. The horizontal tensioning mechanism also includes a weather sealing flap which is closed to seal the side edges of the curtain by rotation of the tensioning rod.