Which line in blueprint reading defines the walls and surface boundaries of prints?

The object line is the primary line type used in blueprint reading to define the walls and surface boundaries of a structure. It is represented as a solid, thick line and indicates the outline and edges of objects in the drawing. This type of line provides clear visual information about the form and shape of the structural components, making it essential for understanding the overall design and layout of the project.

In contrast, other line types serve different purposes. Center lines, for example, are typically thinner and often used to represent the center of circles or symmetrical features, rather than the boundaries themselves. Hidden lines depict features that are not visible from a particular viewpoint, indicating elements that lie behind or within the main structure. Dimension lines are utilized to show measurements and sizes, aiding in the accurate interpretation of distances but do not define the physical boundaries of surfaces or walls. Each line type has its specific function, but it is the object line that fundamentally outlines the structures in question.