Abstract: An element for use in making a reinforced concrete structure of substantially planar shape. The element includes a) at least a lower reinforcing mesh consisting of mutually crossing reinforcing rods (1, 2) rigidly secured to each other, and b) a number of spaced filler bodies (3) of substantially identical shape and size cooperating with the lower mesh (1, 2) so as to locate them in a regular pattern corresponding to the pattern of the lower mesh. These filler bodies (3) interengage (14) with the lower mesh (1, 2) so as to form a rigid body, with the spaced filler bodies cooperating with the reinforcing mesh to provide cavities in the finished structure. The filler bodies (3) include flanges (8) cooperating with each other to form a lower shuttering. Preferably also, an upper reinforcing mesh (1a, 2a) is used, further increasing the rigidity of the element.