NOVELTY - The structure has a rail (20) and a crosspiece (90) extending along longitudinal and transversal directions (X, Y) of a horizontal plane, respectively. A lateral pair of fixation walls (65) is provided with a screwing groove (66) that is opened along vertical direction, opposite to a plane inner surface of a base (21) of the rail. The lateral pair of fixation walls is carried by the base of the rail at a distance, along the transversal direction, from a maintenance part (40) for fixing the crosspiece with the rail. A filling device (160) is installed between the rail and an adjacent rail.    USE - Structure for assembling a solar energy recovery panel i.e. photovoltaic panel, utilized for generating electric energy from sunlight, of a solar energy recovery system (claimed) on a frame i.e. roof frame, of a building. Can also be used for assembling a solar energy recovery panel on other frames such as inclined or straight frame, installed on a facade of a building and floor.    ADVANTAGE - The configuration of the structure allows assembling the filling device without piercing so as to simplify the assembling of a solar energy recovery system and to improve fixation of the filling device, thus allowing the filling device to satisfy the requirements of shock resistance test i.e. 1200 joules test, by retaining 50 kg mass released from height of 2.4 m for stimulating the fall of a body. The same fixation walls are utilized for fixing the crosspiece with the rail, thus standardizing the fixation elements for the structure, and hence simplifying the assembling of the structure.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a solar energy recovery system.    DESCRIPTION OF DRAWING(S) - The drawing shows a partial perspective view illustrating positioning of a rail and a crosspiece in an assembling structure.    Longitudinal direction (X)    Transversal direction (Y)    Rail (20)    Base (21)    Maintenance part (40)    Lateral pairs of fixation walls (65, 110)    Screwing groove (66)    Crosspiece (90)    Filling device (160)