12 Machine Trades Print Reading Copyright Goodheart-Willcox Co., Inc. At fi rst glance, the idea of three-dimensional visualization seems diffi cult to grasp. Multiview drawings, however, will become easier to understand as your visualization skills improve. The following explanations, fi gures, and lessons will help improve your print reading skills. Views in a Glass Box In a conceptual drawing, two viewing planes—a horizontal plane and a vertical plane— intersect to create quadrants. See Figure 2-2A. Each quadrant represents a different viewing angle—fi rst-, second-, third-, and fourth-angle. The viewing angle determines how the views of an object are projected. Only the fi rst- and third- angles are used for drawings because the second- and fourth-angles repeat the same information. The majority of the drawings in this book are third-angle projections. The United States and Canada primarily use third-angle projections for multiview drawings. A drawing viewed and projected from the third quadrant is a third-angle projection. With third- angle projection, the viewer is looking toward the desired view of an object. A viewing plane is located between the viewer and the object. The desired view is transferred onto the viewing plane in front of the viewer. The shape of the object determines how it is shown in a view. Goodheart-Willcox Publisher Visualizing an object in third-angle projection. A—Viewing planes create four quadrants with the third quadrant highlighted. B—An object in a glass box showing third-angle projection. The three primary views project toward the surfaces of the glass box. C—This symbol indicates a third-angle projection. Figure 2-2 A Projectors A B C