Refers to the warrior's wrist bitten by a poisonous snake, which should be cut off immediately to avoid the toxicity spreading to the whole body. Metaphor is decisive, without hesitation and without tolerance.
[Pinyin]
Man surnamed Zhang
[source]
Tang Doushou's Writing a Book: "A gentleman abandons flaws to paint talents, and a strong man breaks his wrist to be all-round."
[near meaning]
Be decisive in your work, and don't do anything wrong.