What is the role of extension lines in a blueprint drawing?

Extension lines play a critical role in blueprint drawings by extending the dimensions beyond the actual size of the part being represented. These lines are essential for indicating where the measurements start and end, providing clarity on the dimensions to be taken into consideration for manufacturing or construction processes.

By extending beyond the physical boundaries of the object, extension lines help in creating a clear visual representation of the dimensions, ensuring that anyone reviewing the drawing can accurately interpret the measurements without ambiguity. This allows for precise cutting, fitting, and assembly of components in manufacturing contexts.

In contrast, the other options serve different purposes that do not align with the specific function of extension lines. Hidden features are indicated using specific types of lines, while colors typically provide information about materials rather than serving as a dimensional reference. Surface textures are indicated through patterns or symbols in the drawing, rather than with extension lines, which focus solely on the dimensioning aspect.