A chink in somebody’s armour

Pro Tip 1/3

The phrase is a metaphor from medieval armor, meaning it's not about actual armor but a person's weak point.

Despite his experience, not adapting to new technology was a chink in his armour.

Pro Tip 2/3

This phrase often implies a weakness that could be exploited by others.

Her short temper is a chink in her armour that her opponents use to their advantage.

Pro Tip 3/3

The weakness described by the phrase may not be apparent at first and could require insight to identify.

He seemed invincible until we discovered a chink in his armour – his fear of public speaking.