This idiom, or a word or phrase that can’t be understood outside its cultural context, frequently trips people up. See what we did there?
The commonly used phrase comes from track and field, where athletes are required to put their foot behind the starting line and wait for the start signal, with their toe just next to the line. Race officials used to yell this phrase instead of what we use now, “On your marks.”
The idiom “toe the line” — not “tow the line” — has come to mean do what is expected or act according to someone else’s rules or expectations.
Example: Some managers just toe the line, which others fight for what they know is right.