What is a projection line used for in drawing?

A projection line serves as a vital tool in technical and graphic communication, providing essential guidelines for constructing the drawing. These lines help convey the spatial relationship and dimensions of objects in a structured manner, ensuring that the components of a drawing are accurately represented from different viewpoints. By using projection lines, drafters can maintain proper alignment and proportions, facilitating the translation of three-dimensional objects onto two-dimensional surfaces. This technique helps in creating clear and precise representations, which are crucial in conveying design intent and technical specifications.

While other options like defining the main feature or outlining solid shapes are important aspects of drawing, they do not specifically cover the purpose of projection lines, which focus on guiding the drafting process rather than detailing or emphasizing features within the drawing.