The gnomon is the part of a sundial which casts the sun's shadow onto the dial plate, which is inscribed with the hourlines. In most sundials, the gnomon consists of a rod, or the side of a triangle, running parallel to the Earth's axis and pointing to the celestial pole.
A vertical sundial , as the name implies, has its dial mounted vertically, usually on the wall of a building. in distinction to a horizontal dial which has its dial plate placed horizontally, either on the ground or on a pedestal.
  Geographical location Dial Type
Horizontal		 Latitude/Longitude
52°41'N 2°27'W
Telford Town Park
 Photo By
P. E. Walker 		British Grid Reference
SJ 698 083
Telford Town Park

This photograph was taken on a bright autumn day in the Town Park, Telford, Shropshire. The sundial is a conventional horizontal dial. What is unusual is its size.

The gnomon stands about 2 metres high and the dial is about 5 metres in diameter. The hour numbers stand about 50 cm. high, just right to act as seats for passers-by !