Functioning of a sundial.
The shadow of an object constantly changes direction because the earth rotates around its axis. If the shadow points north, it is 12:00 in the afternoon. The sun is then exactly above the meridian at the highest point of the day. From there, hour lines can be arranged so that the shadow indicates the hour.
In most sundials, the object that gives shadow is a pole style. This style is parallel to the earth's axis. The style points to the north at an angle to the ground that is equal to the latitude. On some types of sundials, the shadow caster is perpendicular to the plane with the hour lines.
Sundials are almost purchased for a longer period of time and to be placed in the garden as an ornament. They are therefore constantly standing outside, subject to the elements, and the bronze sundial, often placed on a granite pedestal, should be of good quality. We have put together a nice collection for you here.