What are light lines that help check proportion of an object called?

Construction lines

The governing concept is preliminary construction in sketching. Construction lines are light, temporary guides used to plan the size, angle, centre, alignment, and proportion of an object before the final contour is strengthened. For example, an artist may lightly mark a centre axis, basic geometric envelope, or measurement divisions and then compare the height with the width. If the proportions are wrong, these guides can be adjusted or erased without damaging the finished drawing. Therefore option A is correct. Option C refers more closely to the final visible contour, not the initial planning marks. Options B and D are not standard names for proportional guides and do not describe their function. Construction lines may remain faintly visible in a study, but they are normally subordinate to the completed outlines.

This is a Class 9 Art Education question. Chapter: Elements of Art. Topic: Line.