Model-Based Definition > Model-Based Definition > Creating Various Annotation Types > Tolerances > Working with Geometric Tolerances > About Setting Reference Datum > To Set a Reference Datum
  
To Set a Reference Datum
1. Define the active annotation orientation before creating the first annotation in any session.
2. On the Model Tree or in the graphics window, right-click a datum plane or datum axis and click Properties. The Datum or Axis dialog box opens.
◦ Under Type, is selected by default.
 
* You can also open Datum or Axis dialog box by clicking Properties on the shortcut menu that appears when you right-click a datum plane or a datum axis, respectively, on the Model Tree or in the graphics window.
3. If required, type a new name in the Name box of the Datum dialog box and click OK.
 
• You can change the name by choosing Name from the PART SETUP or ASSEM SETUP menu.
• You can blank a reference datum plane only by placing it on a layer and then blanking the layer.
• The On Surface and Define options in the Datum dialog box are used to create 3D datums in drawings.
• To return the datum to its unset state, click .