Three concentric lines curving across the face of the sundial mark the path of the sun. The upper curve is for the winter solstice; the middle one, for the two equinoxes; and the lower one, for the summer solstice. A central vertical line below the gnomon marks the meridian, or noon. Radiating lines on either side mark the hours.
These dials show the hour of the day and the day of the year. On the dial is a gnomon that casts a shadow when the sun is shining. Where the shadow falls determines the reading.