be easily inserted to facilitate the extraction of the panel from concrete thus overcoming the suction effect the plane surface pl is provided with holes pff that serve to house a threaded bar for the purpose of counteracting the concrete thrust produced when the latter is cast into the formwork fig2 a d show a rectangular modular panel where the ribs pnb pnl are made with one type of material for example nylon polyamide while the plane surface pl is made with another type of material for example polypropylene fig3 a d show a rectangular modular panel u2014 presented as one among many possible applications u2014 provided with one or more metal cores am inserted in the ribs pnb pnl and one or more fiber cores af inserted in the plane side pl fig4 a d show a rectangular modular panel u2014 presented as one among many possible applications u2014 provided with some cavities ca designed to serve as structural lightening or stiffening elements and obtained through the injection of gas in the connection points between the ribs pnb pnl and the plane side pl fig5 a d show a rectangular modular panel where by way of example the ribs pnb pnl are lightened and stiffened by cavities cs filled with foamed polymers fig6 a d show a rectangular modular panel where by way of example the ribs pnl are stiffened and strengthened by a metal.