Define Datum References for Geometric Tolerances
1. Select the geometric tolerance instance, the Geometric Tolerance ribbon appears.
2. Under the Tolerance & Datum group, define the Primary, Secondary, and Tertiary references as necessary. The lists contain the currently selected datum and all other datums in the current geometric tolerance model. Click 
to select another set datum or axis.
to select another set datum or axis. | To select a set datum plane or an axis contained in an inheritance feature, click and select the required set datum plane or the axis on the Model Tree or in the graphics window. |
3. To define a composite tolerance, click Composite Frame. Type a tolerance in the Value box and select the desired datum from the Datum reference list:
◦ Primary
◦ Secondary
◦ Tertiary