following the rules exactly. (Alludes to a (numbered) book of rules. *Typically: go ~; do something ~; play ~; run something~.) The judge of the contest ran things strictly by the rules and disqualified us on a small technicality.Everyone insisted that we go by the numbers and not accept the proposal.
Strictly according to the rules, as in Our trip leader is going by the book, allowing us to wander off only for short periods. Shakespeare already used the term figuratively in Romeo and Juliet (1:5): "You kiss by the book." Also see by the numbers.