What does profile of a surface refer to in GD&T?

• A. The shape of a surface boundary, including form and sometimes orientation.
• B. The size tolerance around a surface.
• C. The depth of a surface feature boundary.
• D. The runout of a surface boundary.

Answer: (A)

Profile of a surface sets the intended boundary shape of a surface and defines how far the actual surface can deviate from that boundary. It captures the form of the boundary—how straight or curved, flat or contoured it is—and, when needed, how that surface should be oriented relative to datums. In practice, you’re specifying a theoretical surface that the real surface should follow within a tolerance band, which makes this tolerance all about the shape and alignment of the boundary, not about overall size, depth, or runout. For example, a complex curved housing surface can be controlled to stay within the defined true boundary, ensuring consistent shape and, if datums are used, proper orientation as well.