Typically, these two pieces — dubbed "the main ribs" as compared to the "minor ones" in between them — would fan out a little toward the very end. "Swallowtail" is the name assigned to one specific type of design concerning this end part.

"Controlled spontaneity" is how Wu Jiajun, a pharmaceutical salesman who has been training with Xu during his spare time for the past three years, describes "what it takes to produce that level of artistry that my teacher has arrived at".

"Having the good luck to observe the master while he's at work, I realized that more often than not, the contour of a 'main rib' is decided within a few applications of the carving knife — there's only one knife for the entire process," Wu says.