ace in the hole

/ɐn ˈeɪs ɪnðə hˈəʊl/

/ɐn ˈeɪs ɪnðə hˈoʊl/

ace in the hole

a secret resource, skill, etc. that a person can use to their advantage when the need arises

Examples

1. His ace in the hole is his political influence.

2. Our superior technology is our ace in the hole.

3. She's keeping all the details of their unscrupulous business practices as an ace in the hole should they ever try to fire her.

4. - We have our ice cream truck, and I always say that's our ace in the hole.