A subcutaneous prosthesis subcutaneously implanted within a penis, the prosthesis forming two sides of an elongated cylinder, the sides hinged along top longitudinal edges of their sides. One end of the prosthesis has a gauze sheath providing a means to secure the prosthesis from moving relative to the corpora cavernosa around which it is placed. When the penis is erect it grows in girth thereby causing the two sides of the cylindrical prosthesis to spread divergently and forcing a press-rib against the deep dorsal vein of the penis, thereby restricting blood flow out of the penis so as to improve erectile rigidity and duration.
