A mounting method for mounting a module assembly construction, in particular a photovoltaic plant, of at least two longitudinal supports (11, 12) running in parallel, which are fixed to an underground, and a plurality of module assemblies to be mounted on the longitudinal supports (11, 12), wherein a module assembly mounted on the longitudinal supports (11, 12) extends transversely to the longitudinal supports (11, 12) and respectively connects them, wherein at least one module assembly of the plurality of module assemblies is oriented in a predetermined arrangement on the longitudinal supports (11, 12) in a pre-mounting position positioned on the longitudinal supports (11, 12) and is arranged on at least one displacement device which can be displaced on the longitudinal supports (11, 12) and along a longitudinal direction of the longitudinal supports (11, 12), the at least one module assembly arranged on the at least one displacement device is displaced with the at least one displacement device along the longitudinal direction of the longitudinal supports (11, 12) from the pre-mounting position to a final mounting position positioned on the longitudinal supports (11, 12), and the at least one module assembly is fixed on the longitudinal supports (11, 12) in the final mounting position and thus mounted, and wherein the at least one displacement device is removed from the at least one module assembly in the final mounting position, wherein a module assembly is formed from respectively two transverse supports (21, 22) and a plurality of modules extending between the transverse supports (21, 22), wherein the transverse supports (21, 22) are arranged and oriented towards one another in the pre-mounting position on the displacement device or the displacement device in the pre-mounting position on the transverse supports (21, 22) at a predetermined distance in the longitudinal direction along the longitudinal supports (11, 12), and the modules of the plurality of modules are oriented and fixed in the pre-mounting position on the transverse supports (21, 22). at least one module assembly of the plurality of module assemblies is oriented in a predetermined arrangement on the longitudinal supports (11, 12) in a pre-mounting position positioned on the longitudinal supports (11, 12) and is arranged on at least one displacement device which can be displaced on the longitudinal supports (11, 12) and along a longitudinal direction of the longitudinal supports (11, 12), the at least one module assembly arranged on the at least one displacement device is displaced with the at least one displacement device along the longitudinal direction of the longitudinal supports (11, 12) from the pre-mounting position to a final mounting position positioned on the longitudinal supports (11, 12), and the at least one module assembly is fixed on the longitudinal supports (11, 12) in the final mounting position and thus mounted, and wherein the at least one displacement device is removed from the at least one module assembly in the final mounting position, wherein a module assembly is formed from respectively two transverse supports (21, 22) and a plurality of modules extending between the transverse supports (21, 22), wherein the transverse supports (21, 22) are arranged and oriented towards one another in the pre-mounting position on the displacement device or the displacement device in the pre-mounting position on the transverse supports (21, 22) at a predetermined distance in the longitudinal direction along the longitudinal supports (11, 12), and the modules of the plurality of modules are oriented and fixed in the pre-mounting position on the transverse supports (21, 22).