It is possible to set zero width or height for an adornment allowing it to server as a rule or linear divider on a map. Note that such dividers can only be of horizontal or vertical alignment - not art any angle. It is possible to set both height and width to make a small dot.
The color of the resulting line is the adornment BorderColor. If that is left as the default 'automatic' value, then setting Color for the adornment will give the intended value and may be a more intuitive way of setting it.
The height and or width of a divider is set via its Border attribute (default =2). Thus, a zero-width adornment will draw as unit wide vertical line of height $Height with a width as if there were a persistent border of Border value 1. Conversely, setting a wide value, e.g. 10, causes a 10 wide block of color. In contrast, a default adornment set 10 units wide would show 6 units width of inner color and two 2 unit wide borders. Thus a wide border on a zero-width/depth adornment sets a band of solid single color. If the Border is set to 0, the adornment renders with an overall width and/or height of 1 pixel in Border color.