Various applications are known wherein a portal requires a cover to prevent the passage of wind, rain, light, or anything else through the portal. As used herein portal simply means an opening which would allow the passage of such therethrough, hence a portal may be a window which is transparent to light and the cover of the instant in invention may control the passage of any of the above therethrough. Primarily, the genesis of the present invention resides in the need for large covers for large portals such as may be found on patios, pool houses, green houses, livestock houses, atriums or any other similar structure. The portal may be as small as would accommodate a ventilation fan in a gymnasium or livestock house or as large as an atrium wall in a solar efficient building. The cover may also be used for an inclined roof panel.