Jacob's Rod, also known as Jacob's Staff or Cross Staff, is a navigation tool used by ancient seafarers to determine the angle of elevation of celestial bodies. It is essentially a long staff with a crossbar or a sliding plate fixed at one end. The term 'Jacob's Rod' has now become rare, and more modern terms are used to refer to this tool, such as 'cross-staff', 'backstaff', and 'quadrant'. These tools were made of various materials such as brass, wood, and iron. In modern times, electronic navigation tools have replaced the traditional Jacob's rod, but its significance in maritime history remains significant to this day.
