刻舟求剑刻舟求劍

kè zhōu qíu jiàn

ㄎㄜˋ ㄓㄡㄑㄧㄡˊ ㄐㄧㄢˋ

1lit. a notch on the side of a boat to locate a sword dropped overboard (idiom); fig. an action made pointless by changed circumstances