Wiktionary
hangs by a thread
vb. (en-third-person singularhang by a thread)
Usage examples of "hangs by a thread".
The world hangs by a thread, and myself, I do not wish to fritter away valuable hours prattling about supposed logic or chattering over what every fool and novice knows.
As he is now, it is probable that he never will walk again, and his life hangs by a thread.