The linear grille, System 511beg, from MLL Hamburg, is a linear grille made of aluminium with a free ventilation cross section of 69%. This MLL linear grille is walkable and can thus be used on the ground. It discreetly covers up ducts enclosed in the ground, for example, without blocking them for any necessary maintenance procedures. The system 511beg is equipped with a walkable, rectangular slat of the light series of type 010beg in overlying Frame 501.