Abstract: The improved half-die comprises a concave rigid support describing a chamber superiorly closed by an elastic wall and containing a pressurised incompressible fluid. The chamber internally comprises a lattice which divides it into a plurality of cavities which are interconnected by means of communication holes; each cavity is occupied by an obturator which is solidly anchored to the elastic wall and free of the walls of the relative cavity. Should there be a loss of fluid pressure, which can occur only through an inlet hole and an outlet hole used for introducing the fluid during a construction phase of the half-die and subsequently closed, the obturators prevent any further fluid from exiting during a pressing operation and enable the half-die to keep working.