On the sole of the foot, in the centre of the heel.
Straight insertion 0.3 - 0.5 cun.
Calms the Shen
Relieves pain in the heel
Superficial Innervation: Medial calcaneal nerve branch of the tibial nerve from L4 - S3
Dermatome Segment: S1, S2
Personal experience has revealed this point is a powerful inducer of sleep when massaged. Being on the heel and between Shenmai Bl-62 and Shaohai Kid-6, it may be the original meeting point of the Qiao Mai. It is also the midpoint of the starting points of the two Qiao Mai, between Pucan Bl-61 and Rangu Kid-2. The skin, being thick here, may not have been conducive to needling through the heel, especially if trying to induce sleep, and so its locations were moved to either side. This could suggest that lower locations that can penetrate under the heel to this point may be better than the traditional locations that are just under the malleoli and enter the joint space here.
Basic information on location, needle depth, TCM actions, indications and combinations is taken from Deadman et al (2001): A Manual of Acupuncture with additional anatomical information researched by reference to Gray's Anatomy (38th Ed., 1995) unless otherwise referenced. Images were found on acupunctureschoolonline.com and can be traced back to Claudia Focks (2008) Atlas of Acupuncture originally. I cannot claim any credit or rights over them. Other sources should be quoted in the text.
For some of the more unusual terms I have created a glossary here