Abstract: A novel deployable and stackable accordion shutter system includes an overhead header presenting a track and a laterally disposed abutment surface. The system includes a plurality of trolley supported shutter members which are rotatable about a vertical axis adjacent one edge portion thereof. The system further includes a sill having a guide slot which is disposed beneath the track in alignment therewith. The sill also has an abutment surface disposed in alignment with the abutment surface of the header. The shutter members carry abutment contacting elements disposed for coming into contact with the abutment surfaces to rigidify the structure when the shutter system is deployed. Additional abutment surfaces are provided adjacent the edge of the shutter which is supported by the trolley for further strength. The shutter members are specially configured to facilitate close stacking of the system.