Close to the skin. When taking dental film, the beam limiter is a device to position and fix the dental film, which needs to be in contact with the skin to ensure accurate imaging. The function of the beam-limiting tube is to limit the propagation range of X-rays, so that they can only irradiate specific areas, thus obtaining clear dental images. When using the beam limiter, it is necessary to stick to the skin, ensure the distance between the teeth and the X-ray source is consistent, and reduce the influence of scattered radiation.