fall into line. Adhere to established rules or predetermined courses of action. For example, This idea falls in line with the entire agenda, or It wasn't easy to get all the tenants to fall into line concerning the rent hike. A related term is
bring into line, meaning “to make someone fit established rules,” as in It was her job to bring her class into line with the others. These terms employ line in the sense of “alignment,” a usage dating from about 1500.