This data type is called a Border since it was originally used to create
border lines around display objects.  It is actually a general purpose
structure for drawing connected lines between any series of points.

A Border is easier to use than an Image structure.  Only the following
need be specified to define a border:

  * An internal position component which is used in determining the final
    position of the border.

  * A set of coordinate pairs for each vertex.

  * A color for the lines.

  * One of several drawing modes.

 Border Structure Definition     Border Colors and Drawing Modes 
 Directly Drawing the Borders    Border Coordinates 
 Border Example                  Linking Borders