The weather protection grid, System 742.4, from MLL Hamburg, is a ventilation grid made of aluminium with a free ventilation cross section of 53%. The system 742.4 is equipped with a sliding-water safe, Z-slat of the heavy series of type 040, which in turn is installed in enclosed Frame 702.4 by means of a proven clip technology. The slats fastened with the MLL clip system are also removable afterwards for repair work on on the facade or similar purposes.