toe the line
Definition from Wiktionary, the free dictionary
- From sailing terminology, in which a line refers to a rope or cable that is used to adjust a vessel's sails. Toeing the line means using the toe of one's foot to find the relevant line in order to orient oneself.
- (idiomatic) To abide by the rules or conventions.
- Television shows these days do not always toe the line of decency and common sense.
Usage notes 
- This is sometimes carelessly written as tow the line, which itself has taken on a new meaning as an eggcorn. This practice probably originated with people who heard the expression but were not familiar with the original spelling or meaning. With the spelling tow the expression naturally takes on a slightly more active meaning: not simply conforming to the rules, but helping to enforce or confirm them.