A sharp blade
Blowing hair and sharp blade is a Chinese idiom. Its pinyin is Chu ī m á ol ì R è n, which means to cut off hair with one blow. The sword is extremely sharp.
Idiom usage
Examples
In many martial arts novels, the sharpness of weapons is often described as "cutting iron like mud".
A sharp blade
The danger of participating in business - shēn shāng zhī yú