The meanings of all other attributes depend upon this property, and some are only relevant to some label types.  See the other properties for details.
The Ruler type label produces either a vertical or horizontal scale marker, the orientation depending on which of the Width or Height properties is the larger, and tick marks may be reversed by setting the smaller property negative.  The label is not displayed at all if the image does not contain scaling information, and the size of the marks may, if required, be obtained using the TickSpacing property.