Which type of line in the alphabet of lines conveys the size of an object on a blueprint?

The type of line that conveys the size of an object on a blueprint is an extension line. These lines are used in conjunction with dimension lines to indicate where measurements start and end, effectively guiding viewers to the precise size of the object being depicted. Extension lines often extend from the edge of the feature to be measured and help clarify the exact limits of those dimensions. They can be straight lines that connect to the object and facilitate communication of important size details, making it clear how large or small a component is in relation to others on the drawing. This function is critical in architectural and engineering designs, ensuring accuracy and clarity in the representation of dimensions.