Abstract: A device which stabilizes the sheath of an endoscope or arthroscope during surgery. The device is a relatively thin, flat, flexible plate of plastic material and is adapted to be placed against a patient's body at the area where penetration is made by the scope sheath. The plate is formed with a predetermined sized central hole and the sheath is slidably inserted through the hole and has an interference fit with the surrounding plate material. The plate provides a stable base for the scope to be slidably moved with respect to the plate to adjust the depth of penetration. The plate preferably has a bow or generally figure-eight configuration which provides sufficient surface area at both ends of the plate to provide a stable base for the scope while permitting other surgical instruments to be inserted into the patient's body closely adjacent the scope due to the concavity of the plate sides. Various mechanisms can be mounted in the central plate hole to accommodate various sizes of scope sheaths.