Abstract: A tandem screen assembly for shielding an external area of a building such as a colonnade by attaching a head box to the outside of the building and two pairs of upright guides are at each end of the head box which provide a track for a transparent roller screen and a track for a mesh roller screen side by side so that one screen lies in front of the other in a compact arrangement. The assembly is modified by the inclusion of a mullion which creates a passageway into the shielded area. The pairs of upright guides permit the locking of a screen rail at half height. A screen rail has a handle which shoots bolts in and out of the upright guides to arrest the screens, allowing them to be tensioned by the hand crank or electric motor drive.