A prosthesis is implanted subcutaneously within a human penis, the prosthesis forming sides of an elongated longitudinal modified cylindrical shape, the sides hinged along a common abutment therebetween. A sheath is mounted around the prosthesis' wall and a net sheeting is imbedded under the surface of the prosthesis' wall providing a means to secure the sides; restraining them to further secure a corpora cavernosa around the prosthesis is placed. When the penis is erect it grows in girth thereby causing the sides to diverge, forcing a press-rib against a deep dorsal vein of the penis, which results in restricting blood flow and maintaining erectile rigidity and duration.