We show here the simple window fastening in the roller shutter box with the RK-Fixed-DS-RA. The upward fastening stiffens the window. Sagging of window frame and roller shutter box is prevented and can even be corrected upwards. The RK-Fixed-DS-RA transfers forces such as wind load and the opening and closing of the window sash directly to the interior concrete ceiling or lintel. It is suitable for all box systems.