straight and narrow

Etymology
Probably "strait and narrow," from Matthew 7:14.

Noun

 * 1)  A path of honesty; a procedure according to rules and plans.
 * The project would seriously go down the pan if Mrs. Foster weren't here to keep it on the straight and narrow.

Translations

 * Finnish:
 * French: droit chemin
 * Italian: retta via, in carreggiata
 * Polish: prosta droga, iść prostą drogą, pójść prostą drogą
 * Swedish: den smala vägen