set of bars of maximum lengths fig7 8 9 10 11 and 12 show the steps of assembly of the rolled meshes the first roll is placed on the formwork fig7 and unrolled along the x axis fig8 so that the mesh remains extended along the x axis fig9 the second mesh is then placed fig1 and unrolled along and forming a y axis above the first mesh fig1 thus a bi directional mesh is assembled with minimum waste and at maximum assembly speed fig1 d the meshes are fixed together by means of hooks these hooks may be zigzag stirrups or butcher hooks 5 which articulate and hold together the upper and lower meshes 5 an alternative to the hooks is the steel tumbuckle 10 which articulates and attaches the upper and lower meshes this tumbuckle has an upper fold and a lower shackle 11 to fix the compound made up by meshes and discs and to attach it to the formwork e pouring of the concrete concreting is next carried out thanks to the ample bend radium of the disc sides an optimal concreting may be accomplished by the concrete easily filling the lower sections the ring shaped upper volume of the disc has three interruptions allowing the entrance of the concrete and the filling of the central section of the disc fig2 26 and 27 show the stages of the construction process for the construction of a prefabricated slab b placing the lower steel mesh separated from the bottom by means of plastic spacers the mesh is placed on the formwork with the plastic spacers which lift the mesh and keep it.