A sundial is a device that tells the time of day by the apparent position of the Sun in the sky. In the narrowest sense of the word it will consists of a flat plate, the dial and a gnomon which will throw a shadow onto the surface; lines marked onto the surface will indicate the time of day. The style is the time-telling edge of the gnomon, though a single point or nodus may be used. As the sun appears to move across the sky, the shadow-edge aligns with different hour-lines. The gnomon may be a thin rod, a wire or an elaborately decorated metal casting. The style must be parallel to the axis of the Earth's rotation to remain accurate throughout the year. The style's angle from the horizontal is equal to the sundial's geographical latitude.