Vertically 0.5–1 cun between the artery and the thyroid cartilage.
Caution: Carotid artery, carotid sinus, jugular veins. The carotid artery is located directly at the anterior border of the sternocleidomastoid muscle. The needle should be inserted anterior to where you can feel the pulsating of the carotid artery.
The artery should be held in a lateral position with one finger of the palpating hand above and one finger below the insertion site. Irritation of the carotid sinus can lead to a lowering of the blood pressure and fainting!
Renying ST-9 is an important point.
Like other Window of Heaven points, it is able to ascend and descend Qi to and from the Head. It is particularly widely used when there are Qi Excess on the top part of the body, by subduing the Rebellious Qi.
It is also the Sea of Qi point. By definition, it tonifies Qi. However, in practice, Renying ST-9 is more used to regulate Qi and restore Qi balance between different parts of the Body (eg: Qi Excess in upper part of the body and Qi Deficiency in lower part).
Finally, it dissipates nodules in the neck area. Typical symptoms includes adenitis, nodules on the vocal cords or thyroid swelling.