In an engineering drawing, visible lines are the thick, solid lines that represent the visible edges and boundaries of an object or part. Their purpose is to clearly and accurately depict the shape and size of the object, as well as to distinguish it from any hidden or non-visible features. Visible lines are typically drawn with a standard (thick) line weight and are emphasized to help convey important information about the part being represented. In accordance with ASME Y14.2 standards, visible lines should be drawn with a sharp, consistent thickness (generally .6 mm) and be free of any breaks or irregularities.
