Model-Based Definition > Model-Based Definition > Creating Various Annotation Types > Tolerances > Working with Geometric Tolerances > About Setting Reference Datum > About Setting Reference Datum
  
About Setting Reference Datum
Before you can reference a datum plane or axis in a GTOL, you must set it as a reference. You can set a reference datum using and .
If you set a reference datum using , then Creo Parametric creates a set datum tag and displays the datum name in a box that is attached to the datum. This is the old style display of set datum tag.
If you set the reference datum using , then Creo Parametric creates a set datum tag as a standalone annotation placed on an annotation plane and displays the datum name in a box attached to a solid triangle. This solid triangle is attached to the datum.
The old_style_set_datum configuration option allows you to control the display of in the Datum or Axis dialog box. Set the value of this configuration option to no if you do not want the Datum or Axis dialog box to display . The default for this option is yes.
After you have set a datum, you can still use it in the usual way to create features and assemble parts.