Volume 3, Chapter 5:

Names Associated with the Ch’in Front and Back

In front of the forehead (e) at the side, the form is like an overturned boat.  It could also be said to resemble a crescent moon.   (The area) in the center resembles a tongue.     With the mouth partially exposed, we have the lips and tongue.  On the two sides we have two feet hanging down  that are called wild duck feet (fu-chang鳧掌) or alternatively  peg protectors (hu-chen 護軫).  Behind at the tail, the top part rises up and the bottom slants down.   In the center (of the tail) we have a concave indentation that is broad at the top and narrow at the bottom.  This is where the strings are contained.