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Phrase(s): 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.
McGrawhill's American Idioms And Phrasal Verbs