Abstract: Method of manufacturing this panel by pouring concrete in a mold where a reinforcement has been introduced. According to the method there are first of all provided rectangular molds in which at least two of the opposite sides are flared. Concrete is thereafter poured into one of the molds while introducing the reinforcement and this operation is continued until the mold is completely filled. On the other hand, there are provided steel trusses having seating pads at both ends thereof, each truss being formed of a base and a head connected together by a system of metallic rods mounted in zigzag. Then, the two trusses are spacedly mounted parallel to one another as well as with the two flared sides of the mold, above the surface of the concrete which has been freshly poured in the mold and the head of the truss is caused to penetrate therein by means of a U-shaped winch mechanism until the seating pads of the trusses come flush with the surface of the concrete.