尺蚓穿堤，能漂一邑

Explanation: Earthworm is small, but it penetrates into the embankment, will be able to flood the entire city. Metaphor not pay attention to small accidents, will lead to disaster. 　　Source: Qi Liu day, "Liu Zi Shen new on gap" foot indole crossing dike, can drift a Yap; inch smoke exchange points, resulting in destruction of thousands of rooms. "