square peg (in a round hole) idiom informal
（因个性原因而）与（某职位）格格不入者
a person whose character makes them unsuitable for the job or other position they are in
He never quite fitted in when he was working here - he was always a bit of a square peg. 他在这儿工作时一直都没完全适应——总有点儿格格不入的。