to keep undeviatingly on a
course of
action; to behave in a proper, disciplined or obedient manner, without deviation from
propriety. This
phrase is said to be of
nautical origin, from a test of sobriety
given to sailors. The test consisted of the
sailor being made to
walk the length of a
straight chalk
line drawn along the deck of a
ship. If he could not
walk the length of it, placing each foot directly on the
line, he was judged unfit for duty and was thrown in the brig (a compartment on a
ship where prisoners are confined).