Combination of an installation apparatus and a cover panel, in particular for the installation in apparatus installation ducts, wherein the cover panel on the rear side thereof that faces the installation apparatus possesses first holding devices; the installation apparatus on each of the outer elongate sides thereof possesses in each case one second holding device which corresponds to and interacts with the first holding devices so as to enable the cover panel to be fastened to the installation apparatus; wherein the first holding devices on the rear side of the cover panel are configured as double hooks (21, 31; 21', 31'; 22, 32; 22', 32') formed from two staged latching hooks lying next to one another and are attached such that at least one double hook (21, 31; 21', 31'; 22, 32; 22', 32') engages in each case on the left and the right elongate side of the installation apparatus; wherein each double hook (21, 31; 21', 31'; 22, 32; 22', 32') is composed of a flexible resilient first staged latching hook (21, 21'; 22, 22') and a rigid, non-resilient second staged latching hook (31, 31'; 32, 32') disposed next to the former; wherein the first staged latching hooks (21, 21'; 22, 22') have in each case one oblique latching face (21a, 21a'; 22a, 22a') and the second staged latching hooks (31, 31'; 32, 32') have in each case one rectangular step-shaped upper latching face (31a, 31a'; 32a, 32a'); wherein the second holding device is configured as a lateral outer protrusion (11, 11') which extends in an elongate manner on the installation apparatus and which has in each case one rectangular external edge (11a, 11a') which as a protrusion (11, 11') comes into contact and cooperates with said oblique latching face (21a, 21'; 22a, 22a') of the first staged latching hooks (21, 21'; 22, 22') and said rectangular step-shaped upper latching face (31a, 31a'; 32a; 32a') of the second staged latching hooks (31, 31'; 32, 32') in a force-fitting or form-fitting manner so as to guarantee a secure fastening and a compensation of tolerances T and to fasten in a wobble-free manner the cover panel on the installation apparatus. the cover panel on the rear side thereof that faces the installation apparatus possesses first holding devices; the installation apparatus on each of the outer elongate sides thereof possesses in each case one second holding device which corresponds to and interacts with the first holding devices so as to enable the cover panel to be fastened to the installation apparatus; wherein the first holding devices on the rear side of the cover panel are configured as double hooks (21, 31; 21', 31'; 22, 32; 22', 32') formed from two staged latching hooks lying next to one another and are attached such that at least one double hook (21, 31; 21', 31'; 22, 32; 22', 32') engages in each case on the left and the right elongate side of the installation apparatus; wherein each double hook (21, 31; 21', 31'; 22, 32; 22', 32') is composed of a flexible resilient first staged latching hook (21, 21'; 22, 22') and a rigid, non-resilient second staged latching hook (31, 31'; 32, 32') disposed next to the former; wherein the first staged latching hooks (21, 21'; 22, 22') have in each case one oblique latching face (21a, 21a'; 22a, 22a') and the second staged latching hooks (31, 31'; 32, 32') have in each case one rectangular step-shaped upper latching face (31a, 31a'; 32a, 32a'); wherein the second holding device is configured as a lateral outer protrusion (11, 11') which extends in an elongate manner on the installation apparatus and which has in each case one rectangular external edge (11a, 11a') which as a protrusion (11, 11') comes into contact and cooperates with said oblique latching face (21a, 21'; 22a, 22a') of the first staged latching hooks (21, 21'; 22, 22') and said rectangular step-shaped upper latching face (31a, 31a'; 32a; 32a') of the second staged latching hooks (31, 31'; 32, 32') in a force-fitting or form-fitting manner so as to guarantee a secure fastening and a compensation of tolerances T and to fasten in a wobble-free manner the cover panel on the installation apparatus.