searchsomething with a fine-tooth comb

go over something with a fine-tooth comb & searchsomething with a fine-tooth comb & go throughsomething 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.