The speculum helps keep the mouth open during the exam and helps avoid biting injuries. Hidden categories: The sigmoidoscope can be further advanced into the lower intestinal tract and requires an endoscopic set-up. The best-known speculum is the bivalved vaginal speculum; the two blades are hinged and are "closed" when the speculum is inserted to facilitate its entry and "opened" in its final position where they can be arrested by a screw mechanism, so that the operator is freed from keeping the blades apart.
Large incisor plates increase safety and the opening mechanism is effortless. A weighted speculum is placed in the vagina during vaginal surgery with the patient in the lithotomy position.