3 cun lateral to the lower border of the spinous process of the 12th thoracic vertebra (T12).
How to locate
First locate the spinous process of T7, which is level with the inferior angle of the scapula, when the patient is seated with their arms hanging down. T12 is five thoracic vertebrae below.
Or 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 identify the spinous process of the 12th thoracic vertebra (T12) by counting four up.
Weicang BL-50 is 3 cun lateral to the lower border of T12. Weishu BL-21 is at the same level but 1.5 cun lateral to T12.
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.