Secret-place cakra
Lower terminus of uma
The four-faced secret-place cakra (gsang ba'i 'khor lo) at the perineal floor — the point where the three channels are said to be knotted below and from which uma ascends along the front of the spinal axis. Lower terminus of the central channel in Tsongkhapa's presentation.
Point 4 of 17 in Tibetan Tsa Lung — Three Channels
Cross-tradition overlaps
No overlapping points are registered for this point.
Sources
Tsongkhapa, A Book of Three Inspirations (primary_canonical)
The section describing the channels and cakra seats identifies the secret-place cakra (gsang ba’i ’khor lo) as the lower point at which the channel system is gathered and from which the central channel rises. The perineal coordinate is therefore a schematic rendering of a tantric locus, not a physiological claim.