Translations:TechDraw Geometric dimensioning and tolerancing/68/en

Datums in the GD&T sense of the meaning are surfaces your tolerance is relative to. They are created as Balloon:
 * after adding a Balloon, set End Symbol to Filled Triangle in the balloon dialog.
 * if the bubble shape is not already a frame, set Bubble Shape to Rectangle.
 * drag the bubble with the mouse so that the triangle points away from the datum surface.
 * since it is common to have a straight line for datums unless the datum surface is not perpendicular to X or Y, assure that either the properties and  or  and  are equal to get a straight Balloon line.