“The upper top hung sash (of the window) opens upwards, whereas the lower sash can be tilted forwards, allowing easy access to the balcony recess. When rotated through 0° to 45°, the sash is supported by an innovative auxiliary system which allows leaving the open sash in any position within this range. The upper sash can be raised up to 45°. Side barriers are integrated into the bottom sash and slide out during opening. When closing the lower sash, balcony barriers hide in the window, thus they are not visible above the roof. Concealed under the window flashing elements, they do not collect dirt or spoil the aesthetics of the roof”.
Source and more at: freshome.com