1. After the injured person is lying on his back, the lifeguard must first carefully place his neck in the "median position", that is, the line connecting the head to the corner of the mouth and the earlobe is perpendicular to the ground, and the tip of the nose is in line with the navel;
2. The lifeguard uses a finger to measure the distance of the injured person from the lower corner of the mandible to the clavicle, and then select the neck brace suitable for the injured person;
3. Carefully thread the neck support into the back neck and then. Slowly fit the small dot of the lower jaw pad to the lower jaw of the injured person;
4. Carefully tighten the neck brace and take care to avoid moving the injured person's head and neck and spine.