Abstract: The mounting cross-piece or node assembly serves for the leak-tight connection of the cut ends of profile sections with one another. These profile sections are provided with an upper lengthwise extending opening and thus form a support or carrier construction or framework in the form of a grid or grid structure suspended at the ceiling of a room, especially a clean room. Filter frames and clean room filters can be mounted in gas-tight fashion in the grid structure. The mounting cross-piece assembly comprises at the cut surfaces of the profile sections to be interconnected and at the sides of the mounting cross-piece confronting such cut surfaces connection elements which can be secured in both of these components.