What is the main purpose of using extension lines in dimensioning?

The main purpose of using extension lines in dimensioning is to indicate dimension limits. These lines extend from the points of the feature being measured to show exactly where the dimension begins and ends. This is crucial for ensuring that anyone reading the drawing understands the precise size or location of the features being referenced. By clearly defining these limits, extension lines help eliminate ambiguity, enabling accurate manufacturing or construction based on the provided dimensions.

Connecting points for clarity, illustrating material types, or showing part motion are functions that might be performed by other types of lines or annotations within technical drawings, but they do not represent the primary function of extension lines in dimensioning. Extension lines specifically serve to delineate the extent of a dimension, making it clear what is being measured.