80 Print Reading for Industry Copyright Goodheart-Willcox Co., Inc. • Principle Two. As a result of Principle One, all flat surfaces appear in a multiview drawing as one of the following: • A line, if the orientation is perpendicular. • True size and shape, if the orientation is parallel. • Foreshortened, if the orientation is inclined. See Figure 5-11. • Principle Three. All surfaces appear in every view of a multiview drawing, even if only as a line and even if represented by a hidden line. Three Types of Surfaces If the principles previously discussed are further applied, there are three basic types of flat surfaces that can be defined in an orthographic projection. A normal surface is defined as a sur- face parallel to one of the three projection planes and, therefore, perpendicular to the other two. For example, each surface of a cube is normal and the top flat surface of a cylinder is normal. If normal surfaces are examined with respect to the three principles stated above, the following will apply: • The normal surface appears true size and shape in only one view. • The normal surface appears as a line in two of the three regular views. Very often, when looking at a line in a multiview drawing, the line represents an edge view of a surface. When looking at the front view of a cube, the top and right side surfaces appear as lines. Study Figure 5-12A. With respect to the top edge of the object in the front view, if you only “see” the front edge along the front Goodheart-Willcox Publisher Figure 5-11. A flat surface can appear in a projection as an edge, in true size and shape, or foreshortened. Edge view (looks like a line) True size and shape Foreshortened shape Perpendicular Parallel Inclined Goodheart-Willcox Publisher Figure 5-12. Flat surfaces represented in orthographic projection. A—Normal surfaces appear as either a line or true size and shape. B—Inclined surfaces appear as a line or as a foreshortened shape. T F R A B T F R B C A B A B C A C