The cover is formed as a grillage (1) and consists of a number of rods (3) which are arranged at a distance from each other and in parallel. The rods consist of solid material and are arranged at an acute angle ( alpha ) relative to the axis (A) of the grating. The acute angle may be 45 deg and a number of small rods (5) may also be provided at the ends of the grillage so that they connect neighbouring rods.
