a Cantonese idiom which describes someone who is flexible enough to adapt to the circumstances of an emergency situation
Definitions (粵典–words.hk)
語句
非常時期，就應該彈性咁用非常手法處事 to be flexible; to adapt to circumstances in an emergency (a reference to the rules of Chinese chess); literally: in a crisis a horse can move in the field
Definitions (Wiktionary)
phrase, idiomatic
to take extraordinary actions in an emergency