Fig. 24.
By projecting the lines back on the vertical, and down on the horizontal plane, we obtain two views which are respectively the elevation on the vertical and the plan on the horizontal plane; to obtain the third view or end elevation, we have another plane placed perpendicular to planes H and V, as shown in Figs. [23] and [24], and the lines projected back from the left end; by opening or revolving these planes into one plane, as shown in [Fig. 25], we have a working drawing made in the 1st angle.
Fig. 25.
Referring to [Fig. 24], where we placed the solid in the 3rd angle, we project the lines up on the horizontal and to the front on the vertical plane, and by placing another plane at the end, perpendicular to the H and V planes, we obtain the third projection. Revolving the planes into one plane (i. e., a sheet of paper) [Fig. 26], we have the working drawing in the third angle. Compare the results obtained, and note the difference in the reading of the drawing.
In the first angle we see the plan is below the elevation, and in the third angle the plan is above; the pieces cut out of the exercise may also be noted in the end projection by the lines passing through the center of the exercise; in the first angle the line comes out full, the end being exposed, and in the third angle the surface is behind the full end and shows a dotted line.
Lines that are seen are shown as full lines.
Fig. 26.
Lines that are below a surface and are required in the reading of a drawing are shown as dotted lines.