The invention relates to a retainer for laterally fastening a guide groove for energy supply chains to a structure. The retainer has a support for a bottom area of the guide groove and a position fixer for the guide groove and extends with a vertical section to the side of an intended accommodating space for the guide groove, in which first fastening elements for fastening the retainer at the height of the vertical section laterally to the structure are provided. The retainer has additional fastening elements, which are arranged at a distance from the support in the vertical direction for support and which are designed to engage on the guide groove in a form- and/or force-closed manner. The invention further relates to a retaining system having the retainer.