The views that are presented when determining all the factors necessary to build "anything" are very important to the process. They help to add one more perspective to clarify the intent of the designer, architect, or builder.  Engineered parts rely heavily on this perspective called orthographic projection.  It is a 2 dimensional view that is sometimes integrated with 3 dimensional characteristics.  Various types of lines are often used in these views.  In construction, these views are called flat plane views and are incorporated throughout the graphic developement of a build project and are known as elevations.  Click on the large picture to view an "alphabet of lines" presentation and the pictures below to view info on orthographic projections.