石橋を叩いて渡る (いしばしをたたいてわたる): being excessively cautious; knocking on a strong stone bridge before crossing it

being excessively cautious; knocking on a strong stone bridge before crossing it

Caution past the point of usefulness: tapping a stone bridge to test it before crossing. Usually teasing, occasionally admiring.

A Japanese proverb (ことわざ)