294 Geometric Dimensioning and Tolerancing Copyright Goodheart-Willcox Co., Inc. Orthographic View 0.2 Wide perpendicularity tolerance zone 90° SECTION A-A Meaning Possible orientation of feature axis Datum axis A SECTION B-B No orientation control Model View Goodheart-Willcox Publisher Example 7-11. Specifying perpendicularity of a feature axis relative to a datum axis.