The divider was used to transfer measurements, read distances, and plot courses on sea charts. The instrument's legs comprise a semi-circular section and a straight tipped section. By pressing their fingers on the sections, users could open and close the divider with one hand. The instrument also served to roughly estimate the maximum altitude of a star above the horizon. This was useful for determining the latitude reached during navigation. The observer would hold the divider at arm's length, placing one tip over the star and the other over the horizon. By placing the divider against a graduated circular scale whose radius was equal to the length of his arm, the observer could convert the compass opening to degrees of latitude.