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?
go over/through something with a ˌfine-tooth ˈcomb
(informal) search or look at something very closely or carefully: I went through the accounts with a fine-tooth comb checking for mistakes.The police went through his room with a fine-tooth comb.