The attachment has a frame (1) comprising an external wall that forms a cavity, and cross beams arranged in the cavity. The frame comprises two segments (2) that are connectable or connected with one another. A sheet metal is installed at the external wall for covering recesses (3) in the external wall, where thickness of the external wall is 4-6 mm. The frame and/or the segments are made of light metal i.e. aluminum, or plastic and manufactured by of light alloy welding method or plastic spraying method.
