In the 4th intercostals space, at the very centre of the nipple.
The point is not used for acupuncture and moxibustion, it serves only as a landmark for locating acupoints on the chest and abdomen.
Acupuncture and moxibustion prohibited. Used for measuring the transverse distance of the points on the chest and abdomen. The distance between the two nipples is taken as 8 cun.