Parts of a Sundial – Gnomon, Style, Dial Plate, Hour Lines

All 11 parts on the diagram

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Start here: 7 main parts 7

Gnomon The upright piece that casts the shadow.
Shadow The shade the gnomon throws; its edge shows the hour.
Pedestal The stand a garden sundial is fixed on.
Style The edge of the gnomon whose shadow marks the time.
Dial plate (dial face) The flat surface that carries the hour lines and catches the shadow.
Hour lines The lines the shadow reaches at each hour of the day.
Numerals The hour numbers at the ends of the hour lines, often Roman.

The sundial from the side 1

Substyle The line on the plate directly beneath the style.

The dial plate from above 3

12 o'clock line (noon line) The hour line for noon; on a horizontal dial it runs north.
Center of the dial Where the style meets the plate; the hour lines start here.
Motto A short saying engraved on the dial, usually about time.

How this list was compiled: Read 2026-09-30; a name is kept only where two of these use it. (1) Wikipedia, Sundial and Gnomon: the dial face or dial plate; the gnomon is the entire object that casts the shadow; the style is the gnomon's time-telling edge, parallel to the Earth's axis, its angle from the horizontal equal to the latitude; the substyle is the line on the dial plate straight beneath the style; hour lines; the noon line; Roman numerals; mottoes such as I count only the sunny hours; horizontal dials on pedestals in gardens; sundial time differs from clock time by the equation of time, longitude and daylight saving time. (2) Encyclopaedia Britannica, 11th edition (1911), Dial and Dialling, https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Dial : the style, in the meridian plane at an angle equal to the latitude of the place; the point where the style meets the dial is called the centre of the dial, from which all the hour-lines radiate; the XII o'clock line; the dial plate; the pedestal. (3) Mrs. Alfred Gatty, The Book of Sun-Dials (1900), https://archive.org/details/booksundials00gattgoog : gnomon, style, dial-plate and dial face, hour lines, the substile (or substyle) drawn under the gnomon, the centre of the dial, the twelve o'clock line, numerals, pedestals, mottoes. (4) Alice Morse Earle, Sun-dials and Roses of Yesterday (1902), https://archive.org/details/cu31924019506850 : the stile or gnomon cut to the latitude of the place, dial-face, hour lines, Roman numerals, pedestals, mottoes. (5) T. G. W. Henslow, Ye Sundial Booke (1914), https://archive.org/details/yesundialbooke00hensuoft : a horizontal garden dial is a metal plate with the hours and a motto engraved and a metal gnomon for casting the shadow; hour-lines; pedestal dials; read the time at the edge of the shadow. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work

How it works

A sundial has no moving parts: the Sun does the moving. These are the names dial makers use for the piece that casts the shadow and for the plate that the shadow falls on.

Read the full guide

What casts the shadow

The gnomon is the upright piece. Only one edge of it tells the time: the style, the sloping edge, which points at the sky's pole. The line on the plate directly under the style is the substyle. The shadow falls on the side away from the Sun. A garden sundial stands on a pedestal.

On the dial plate

The dial plate is the flat face. Hour lines fan out from the center of the dial, the point where the style meets the plate, to the numerals at the rim. The 12 o'clock line is the one the shadow lies along at noon. Many dials carry a motto about time.

The style slopes at the same angle as the latitude of the place the dial was made for.
Morning hours are on the west side of the plate; afternoon hours are on the east.

Questions and answers

What are the parts of a sundial called?

The gnomon casts the shadow, and its sloping edge is the style. The shadow falls on the dial plate, which is marked with hour lines and numerals. A garden sundial stands on a pedestal, and many carry a motto.

What is the pointer on a sundial called?

The gnomon. On a garden sundial it is usually a triangular blade standing on the plate. The sloping edge that actually marks the time is called the style, so the two words are often used for the same piece.

Why is the gnomon tilted?

So that its sloping edge, the style, is parallel to the Earth's axis. The angle between the style and a level plate equals the latitude of the place, and the gnomon is set pointing true north in the Northern Hemisphere.

Why does a sundial not match my watch?

A sundial shows Sun time. Clock time differs from it by a few minutes that change through the year, by your distance east or west within your time zone, and by one hour when daylight saving time is in force.

What is written on a sundial?

Besides the hour numerals, often a motto: a short saying about time. One of the best known is "I count only the sunny hours." Collections of sundial mottoes have been published for centuries.