Toe the line/mark

Toe the line or toe the mark has come to mean to conform to set or agreed procedures or standards. If one did not toe the line, one would be said to be out of line. Toeing the line or mark must be very ancient but is first cited in English from the 18th century. A line was scratched or marked on the ground to mark the starting point of a race or boxing match, where the competitors would toe the line or mark. These variations have been used in the figurative sense since the early 19th century and phrases like up to scratch or up to the mark derive from the same source. See also Toe to toe and Up to scratch/up to the mark.