Rulers must be run in the same thread which manages the main content. The VisRuler messages which deal with mouse positions receive the mouse location parameters on the stack, and thus the handlers must be running in the same thread as the callers. This is not a major restriction: since mouse events are so common, sending them across threads to be processed would lead to slow, jerky responses.

</P>
<P>
Your application may also include other objects:</P>
<UL>
<LI>
RulerTypeControl to allow the user to use 