A broken line of medium thickness that shows interior detail not visible from the outside of the part.

A broken line of medium thickness that shows interior detail not visible from the outside of the part.

• A. Hidden Line
• B. Phantom Line
• C. Center Line
• D. Boundary Line

Answer: (A)

In engineering drawings, a hidden line is used to reveal edges or features that aren’t visible from the outside of the part. It is drawn as a medium-thickness broken line, with short dashes spaced to show interior detail like holes or interior steps. The description matches this purpose exactly, since it refers to interior detail that isn’t visible from the exterior. Boundary lines outline the outer shape, center lines indicate symmetry or axes, and phantom lines show features in alternate positions or hidden in another view, so they don’t fit the description as well.

In engineering drawings, a hidden line is used to reveal edges or features that aren’t visible from the outside of the part. It is drawn as a medium-thickness broken line, with short dashes spaced to show interior detail like holes or interior steps. The description matches this purpose exactly, since it refers to interior detail that isn’t visible from the exterior. Boundary lines outline the outer shape, center lines indicate symmetry or axes, and phantom lines show features in alternate positions or hidden in another view, so they don’t fit the description as well.