The phrase 'Saved By The Bell' is used when one has been saved by the timely intervention of something or someone, or when one has been rescued from difficulty at the last second.
Example of Use: “I couldn’t prevent myself from explaining her absence any longer, but then Jill showed up and I was saved by the bell.”
Interesting fact about Saved by the Bell
The expression 'saved by the bell' is an allusion to the bell that is rung at the end of each boxing round. If the bell rings before a knocked-down boxer is counted out, it allows him to get up and move to the fight’s next round.
