Severe Exchange

Lidui, 厉兑, is the last point of the channel, at the nail corner of the second toe. 厉 (厲) can be read as “steep,” “abrupt,” or, by equivalence with 濿, as the high bank of a river; 兑 (兌) is the mouth, the orifice, and also one of the eight trigrams of the Yijing (Book of Changes). In the Yijing commentary called Shuo Gua (說卦傳), the Dui trigram is associated precisely with the mouth: «兌為口».

Two readings follow from this. The anatomical one sees the point as the abrupt edge of the channel, at the tip of the toe. The symbolic one, via the Yijing, links 兌, mouth, with the point's indications in disorders of the mouth and throat, such as toothache. It is a suggestive hypothesis, but no ancient commentator applies it to this point, so it should be taken with caution.

The Lingshu (Spiritual Pivot), chapter Ben Shu (本輸), places it at the beginning of the channel's sequence of the Five Shu points: «胃出於厲兌». It is the Jing-Well point (井穴), which in the Yang channels corresponds to Metal. Because of this status as the Well point of a Yang channel, the tradition has used it in patterns of extreme Heat and loss of consciousness. From here, the Qi rises through ST44 and ST43.