by the book
From Longman Dictionary of Contemporary Englishby the bookby the bookOBEYexactly according to rules or instructions She feels she has to go by the book and can’t use her creativity.do/play something by the book The police were careful to do everything by the book. → bookExamples from the Corpusdo/play something by the book• He plays it by the book.• I do it by the book.• They play it by the book - their book not mine.