Diagram Templates are used every time you start a new OmniGraffle document. If you start a new document by using the File | New menu command, or the⌘+N keyboard shortcut command—a default Diagram Template is used.
OmniGraffle comes with a few templates built in. You can take a look at these templates by using the File | Template Chooser—or use the ⇧+⌘+N keyboard shortcut.
If you choose a to create a new diagram based on one of the templates in the template overview—you'll get a new diagram containing the shapes you saw in the overview. Using templates can be a big time saver.
Templates contain not only the size of your canvas, ...