Visible lines are primarily used for what purpose in technical drawings?

Visible lines are utilized in technical drawings to illustrate the shape and outline of objects clearly. They provide a definitive representation of the object's boundaries, allowing anyone interpreting the drawing to see the external form and dimensions in a straightforward manner. This is vital for creating accurate representations of parts that will be built or assembled, ensuring that the shapes are correctly understood during the fabrication process.

Additionally, visible lines help convey the overall design intent and are fundamental in establishing a visual reference for the viewer. Their clear depiction contrasts with other line types used for different purposes, such as hidden lines that indicate features not visible from the outside or centerlines used for symmetry. By serving the primary role of defining the object's contour, visible lines lay the groundwork for all further interpretation and detailing that follows in more complex technical drawings.