What type of line is used to indicate an invisible edge of an object?

The type of line used to indicate an invisible edge of an object is a dotted line. These lines represent edges that are not directly visible due to perspective or obstruction, yet are important for understanding the shape and features of the object in architectural and engineering drawings. Dotted lines are effective in conveying this information without creating confusion with solid or dashed lines, which serve different purposes in technical drawings. Solid lines typically indicate visible edges or outlines, while dashed lines often show hidden or sectional views rather than invisible edges specifically. Thus, the choice of a dotted line is appropriate for depicting invisible edges, enabling clear communication of design intent.