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Tongshen Cun (Same-Body Inch) refers to a measurement method consistent with the individual's own body dimensions. People vary in height and weight, so the horizontal and vertical measurements of acupoints cannot be uniform. If the Zhongzhi Tongshen Cun Method (Middle Finger Same-Body Inch Method) were applied indiscriminately, it would lead to errors: for thin individuals with long fingers, the measurement would be too large; for obese individuals with short fingers, it would be too small. Therefore, one must measure according to the specific physical constitution to ensure accuracy. As stated in *Biao You Fu* (Marking the Profound): "When selecting five acupoints, using one as a reference must be precise; when selecting three meridians, using one as a reference allows for correction." This implies correcting a meridian by its neighboring meridians and an acupoint by its neighboring acupoints. It is akin to the method of phonetic notation in Chinese characters, where an initial sound and a final rhyme are combined to produce the correct pronunciation. In this way, the true nature of meridians and acupoints becomes clear. Thus, head measurements must be taken from the head, abdominal measurements from the abdomen, back measurements from the back, and limb measurements from the limbs, averaging their lengths and sizes to achieve the Tongshen Cun method. This method is detailed in the preceding sections. Although the later "Zhongzhi Tongshen Cun Method" should not be used indiscriminately, there are specific instances where it is appropriate, which are listed below.

For men, use the left hand; for women, use the right hand. Bend the thumb and middle finger so that their tips touch, forming a ring. Measure the distance between the two ends of the transverse crease at the middle phalanx of the middle finger as one cun. This method is used only for measuring the limbs and the horizontal width of the back where other proportional methods are not applicable; it should not be mixed with other contexts.

The *Gu Du Pian* (Chapter on Bone Measurements) states: "For a person seven chi five cun tall, what are the sizes and lengths of their bone joints?" Bo Gao replied: "The circumference of the skull is two chi six cun." Generally, ancient chi were smaller; approximately one ancient chi equals eight modern cun. Therefore, the mentioned seven chi five cun corresponds to six modern chi, and two chi six cun corresponds to two chi eight fen modernly. The rest follows this pattern. However, individuals with larger bones will exceed standard measurements, while those with smaller bones will fall short. When using proportional measurement methods, adjustments should be made based on the individual's size to achieve optimal accuracy.