The traverse board was used in dead reckoning navigation to record the
course of a ship during a watch period. It consisted of a piece of
wood marked out with a compass rose and eight holes bored along each
point of the compass. Every half-hour (by sand-glass) a peg was
inserted into a hole marking the compass point on which the ship had
run. At the end of the watch the mean course during the watch was
determined from the positions of the eight pegs.