What is a profile of a line tolerance?

• A. A tolerance that defines the boundary for the entire surface.
• B. A tolerance that controls the true form of the line boundary along its length.
• C. A tolerance that confines the true form of a line boundary along its length.
• D. A tolerance that ensures two lines are parallel.

Answer: (C)

A profile of a line tolerance defines a tolerance zone that confines the true form of a line boundary along its length. In GD&T, this means the actual path of that line must stay within the specified profile along every point along the line, so the line’s true form is limited as it extends. This is different from tolerances that apply to a surface as a whole or that enforce parallelism between lines, which is not what a profile of a line controls. The phrase about confining the true form along the length best captures how this tolerance governs a one-dimensional boundary from start to end.