Chapter 7 Orientation Tolerances 299 Copyright Goodheart-Willcox Co., Inc. Perpendicularity of Line Elements A perpendicularity tolerance can be used to control single line elements of a surface, rather than the entire surface. When any single line element of the surface is held per- pendicular to a datum, the note EACH ELEMENT is placed below the feature control frame, as shown in Example 7-16. Orthographic Views Meaning Possible orientation of feature axis Datum plane A 0.15 Wide perpendicularity tolerance zone Goodheart-Willcox Publisher Example 7-15. Specifying perpendicularity of a center plane relative to a datum plane.