Final answer:
A phantom line is drawn below the dimensional value on older drawings to indicate a change in dimension without a corresponding change in geometry, ensuring that it is clear the drawing is no longer to scale.
Step-by-step explanation:
For older drawings created before CAD systems, when a dimensional value is changed without altering the actual geometry, a standard practice is to denote this on the drawing to prevent misinterpretation. The correct answer to the question is that a phantom line may be drawn below the dimensional value to indicate it is no longer to scale. This phantom line usually consists of two short lines at either end, connected by a long line that is broken into a pattern of long and short dashes. It's important to follow such conventions to maintain clarity in engineering drawings, especially when they are not updated to reflect changes in dimensions or scales.