By The Skin Of One's Teeth

Do you feel lucky?

(Hmph, something or rather someone has come to mind. He will not be feeling lucky.)

Well, if you manage to escape by this much then you're pretty lucky in my book.

Meaning
Basically, if you escape something by the skin of your teeth, then you've had a very narrow escape.

Use in Normal Speech
When describing a lucky escape.

"Phew! I just escaped him by the skin of my teeth. Five seconds more and Lord knows what would've happened next."