Working With Model Items and Diagrams > Working with diagrams > Editing diagrams > Equally spacing items on a diagram
  
Equally spacing items on a diagram
1. Select the items that you want to space equally.
2. On the Diagram menu, point to Space Evenly, and then click Horizontally or Vertically.
If the results are not as you want, on the Edit menu, click Undo.
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The Common Diagram toolbar has buttons for each of the spacing commands.