square peg in a round hole
Also, round peg in a square hole. A misfit, especially a person unsuited for a position or activity. For example, Ruth doesn't have the finesse for this job; she's a round peg in a square hole. This idiom, with its graphic image of something that cannot fit, dates from about 1800.
Words nearby square peg in a round hole
square number,
square of opposition,
square off,
square one,
square one's shoulders,
square peg in a round hole,
square piano,
square rod,
square root,
square sail,
square serif