A vertical disc had a graduated (2*23.5º) to six intervals arc corresponding to the six pairs of the zodiac signs (months). Around the centre of the disc rotated a base (with an indicator for its alignment according to the current season) consisting of a vertical gnomon and a curved rod (=scale of the hours) graduated to six estimated intervals. On its periphery it had graduations of a 90º arc, so that the instrument could be hung from the point corresponding to the angle indication of the latitude of the area where it was being used. During its operation the instrument suspension hook turned (around a hypothetical vertical axis) to the East for the indication of the 6 ante meridian hours and to the West for the indication of the 6 post meridian hours. The sunrise and the sunset coincided with the gnomon base while midday with the opposite top.