Abstract: The present invention relates to fastening elements for guide rails at the support rails of a component carrier which is provided to accommodate printed circuit boards equipped with electrical components. The fastening elements are configured as U-shaped spring bars and include a fixed U leg attached to the underside of the guide rails and a free, resilient U leg which is oriented toward the longitudinal web of the support rails. The resilient U leg permits easy insertion of the guide rails into the support rails. The dimensions are such that, after insertion of the guide rails, the resilient U leg stands on the longitudinal web and thus the guide rails are tightly locked against being pulled out.