He does not know his ass from a hole in the ground.
know one's ass from a hole in the ground
idiomTo have an adequate level of knowledge or skill; to understand what one is doing or talking about.
The new manager is clearly unqualified because he does not know his ass from a hole in the ground regarding our software.
Despite his confident tone, it quickly became apparent that the consultant did not know his ass from a hole in the ground when faced with the actual technical data.
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abound in one's own sense
To follow one’s own inclinations and opinions.
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ace in the hole
Synonym of ace up one's sleeve.
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ace up one's sleeve
A surprise advantage of which others are not aware.
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act one's age
To behave in a manner appropriate to one's age.
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act one's age, not one's shoe size
Synonym of act one's age (“to behave in a mature manner; to avoid being childish”).
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afraid of one's own shadow
Exceptionally timid.
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air one's dirty laundry in public
To reveal one's sordid secrets to the public.
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air one's dirty linen in public
Synonym of air one's dirty laundry in public.
Last updated July 12, 2026