go over with a fine-tooth comb

go over (something) with a fine-tooth comb

To scrutinize something; to look at something very carefully. We need to go over these files with a fine-tooth comb to find that missing paperwork. Make sure to go over your thesis with a fine-tooth comb before you hand it in—you don't want your advisors wading through proofreading errors, do you?
See also: comb, go, over
Farlex Dictionary of Idioms.

go over something with a fine-tooth comb

 and search something with a fine-tooth comb; go through something with a fine-tooth comb
Fig. to search through something very carefully. I can't find my calculus book. I went over the whole place with a fine-tooth comb. I searched this place with a fine-tooth comb and didn't find my ring.
See also: comb, go, over
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

fine-tooth comb, to go over with a

To search for or investigate with scrupulous care. Although combs have been known since the time of ancient Egypt, and presumably some had finer teeth than others, the term “fine-tooth comb” dates only from the first half of the nineteenth century. The transfer of combing out nits to other kinds of search or investigation took place only in the late nineteenth century.
See also: go, over
The Dictionary of Clichés by Christine Ammer
See also:
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a straw will show which way the wind blows
  • a crack at (someone or something)
  • all right
  • (you) wanna make something of it?
  • all for the best
  • a thing of the past
  • a slew of (something)
  • a bird in the hand