Which type of line serves as a guide while sketching or drawing?

A construction line is used primarily as a guide in the sketching and drawing process. It is typically drawn lightly and serves the purpose of helping to establish the proportions and layout of the design. These lines are not part of the final drawing; instead, they assist in the overall composition and help sketch out the framework of the object being depicted.

In contrast, object lines are used to represent the actual outline of an object, hidden lines indicate edges not visible in the current view, and center lines denote symmetry and axes of rotation. While all these lines serve important functions in technical drawing, the construction line specifically assists in the initial sketching phase, making it essential for accurately laying out the overall design.