2013

 Name a viewport arrangement so that you can reuse it on the Model layout
or insert it on a named layout.
Setting up different coordinate systems in individual viewports is useful if you
typically work on 3D models. See
Assign UCS Definitions to Viewports (page
151).
Split and Join Model Space Viewports
The illustrations below show several default model space viewport
configurations.
You can easily modify model space viewports by splitting and joining them.
If you want to join two viewports, they must share a common edge of the
same length.
Select and Use the Current Viewport
When you use multiple viewports, one of them is the current viewport, which
accepts cursor input and view commands.
When a viewport is current, the cursor is displayed as crosshairs rather than
an arrow, and the viewport boundary is highlighted. You can change the
current viewport at any time except when a View command is in progress.
To make a viewport the current viewport, you click inside it or press Ctrl-R to
cycle through the existing viewports.
Display Multiple Views in Model Space | 83