ACTIVE lets you change the active instance in a layout.
You know an instance is active when CADKEY surrounds it
with a dashed highlighted box. Only one instance can be
active at a time. 

If you want to change something in an instance that is not
active, you must first make it active.

To change the active instance CADKEY prompts you to choose
the drawing instance you want to make active. Cursor 
select an instance. CADKEY highlights the new active
instance by surrounding it with a dashed highlighted box.

To turn the active instance off CADKEY prompts you to 
choose the drawing instance you want to make active. 
Cursor select in an empty area of the screen, away from 
any drawing instances. CADKEY turns off any active
instance; none of the instances are surrounded by a
highlighted box.
