{v. phr.} To be careful, thorough, and pay close attention to detail. * /"The best way to get an A on the final exam," the teacher said, "is for every one to dot the i's and cross the t's."/ Compare: MIND ONE'S P'S AND Q'S.
DOT THE I'S AND CROSS THE T'S
Meaning of DOT THE I'S AND CROSS THE T'S in English
Dictionary of English idioms . Словарь английских идиом. 2012