A thousand-mile embankment collapsed in an ant hole
Explanation: A thousand-mile embankment collapsed due to a small ant hole. It means that if you don't pay attention to small things, it will lead to disaster or serious losses. Collapse: collapse. Anthill: The burrow of ants. Source: Pre-Qin Dynasty Han Fei's "Han Feizi·Yu Lao": "A embankment of a thousand feet collapses in an ant nest, and collapses in the nests of ants; a room a hundred feet in size is burned by the smoke from the gap."