The use of the patient's fingers to define one cun is one of the commonly used methods to locate acupoints in clinical practice. In the books of the acupuncture

the applicability of the three kinds of finger cun varies according to anatomical regions. According to the authors' statistical data

the length of the three kinds of finger cun is the same

but the length of one cun defined by the proportional measurement method in different parts of the body is not the same. According to the result of the authors'research

the use of the finger measurement method is only applicable for acupoints where proportional measurement method or the use of anatomical landmarks is not convenient.