"Making the Wooden Ox" provides detailed external dimensions, such as "Ribs: three feet five inches long," but makes no mention of the mechanism that operates the legs. This is generally explained as the deliberate withholding of a military secret.
一般人認為「做木牛流馬法」上的記載，不是「肋長三呎五寸」，就是「孔長一寸五分」… …，對外型敘述雖詳，但腿部機構卻無著墨，是有意不傳軍事機密。