Chapter 7 Orientation Tolerances 297 Copyright Goodheart-Willcox Co., Inc. SECTION A-A Meaning Possible orientation of feature axis SECTION B-B Datum center plane B Possible orientation of feature axis ∅0.2 Perpendicularity tolerance zone ∅0.2 Perpendicularity tolerance zone Datum axis A 90° 90° Orthographic Views Model View Goodheart-Willcox Publisher Example 7-13. Adding a slot identified as datum feature B to the length of the ∅25 cylinder. Specifying a cylindrical tolerance zone in the feature control frame and including datum B as the secondary datum establishes the desired resistance for the degrees of freedom of the part.