Gnomon is parallel to the Earth's axis and usually is called a style.
Any visible mark on the style is called a node and, beeing placed at the known height above the dial, is used to indicate Sun's declination, thus, Sun calendar.

An imaginary equatorial dial projection is used to draw hour lines for horizontal sundials with polar style. As a result hour line angles vary for different latitudes seriously. But hour marks 6, 12 and 18 will allways correspond to cardinal directions as West, South and East (in the Northern hemisphere).

The following excel sheet can be used for accurate calculations.

Horizontal sundials with polar style are not universal.
Nevertheless, sundials made for a certain latitude (on the picture φ=45°) may be tuned for proper usage at another latitude by rotating dial plane in East-West axis.