At the level of the 4th posterior sacral foramen, 1.5 cun lateral to the posterior midline.
How to locate
First identify the Tuffier's line which connects the highest points of the iliac crest. The spinous process of the 4th lumber vertebra (L4) mostly falls on this line.
Then palpate in an inferior direction, passing L5, and reach the most superior 1st sacral foramen. Palpate further down for three sacral foramens and locate the 4th one in a depression.
Locate Baihuanshu BL-30 at the same level of the 4th sacral foramen and 1.5 cun lateral to the posterior midline.
Points located between Fufen BL-41 and Zhibian BL-54 are in the lateral branch of the Bladder Channel, while these between Fengmen BL-12 and Baihuanshu BL-30 are in the medial branch.