From Longman Dictionary of Contemporary Englishfine-tooth combˌfine-tooth ˈcomb noun → go through/over something with a fine-tooth comb
Examples from the Corpus
fine-tooth comb• I want to take a handful of good men and go over it with a fine-tooth comb.• I went over it with a fine-tooth comb.• Your lads have been over this place with a fine-tooth comb. 