Which of the following is an orientation tolerance?

• A. Perpendicularity
• B. Flatness
• C. Cylindricity
• D. Runout

Answer: (A)

In GD&T, orientation tolerances control the angular relationship of a feature to a datum. Perpendicularity specifically enforces a 90-degree relationship between the feature’s orientation (often the feature’s axis or a surface) and a datum plane or datum axis. It is a pure orientation requirement: it tells you how the direction of the feature must align, not how flat or cylindrical the surface must be.

Flatness is a form tolerance—it's about how much a surface deviates from being perfectly flat, not about its orientation to a datum. Cylindricity focuses on the shape of a cylindrical feature, controlling circularity and straightness of the axis, which is mainly a form requirement with some axis alignment implications but not a direct orientation to a datum. Runout is a composite that blends form deviation and orientation as the part rotates, so it’s not a pure orientation tolerance either.

Therefore, the best answer is the one that specifies a pure orientation constraint: the perpendicularity tolerance.