By the skin of your teeth

Barely managing to succeed or survive; achieving something with very little margin for error.

This phrase comes directly from the Book of Job in the Bible (19:20): 'My bone cleaveth to my skin and to my flesh, and I am escaped with the skin of my teeth.' Since teeth don't actually have skin, the original Hebrew likely referred to the thin membrane around the gums, emphasizing how close Job came to complete destruction.