The boundary wall has elongated components (1,2) with a base body (3), where the components are connected with each other. The base body has end sections with integral connecting elements (4) for receiving of coupling elements (5). The end sections protrude at the front side of the base body. The components have units for positive reception of a stiffening coupling element (7) connecting the components with each other or with other components. The units are formed as one-sided open slots or grooves in the connecting elements.
