Hidden edge lines are drawn with short dashes and are used to show hidden features of an object. A hidden line should begin with a dash in contact with the line from which it starts, except when it is the continuation of an unbroken line. (See fig. 3-26.)

To prevent confusion in the interpretation of hidden edge lines, you must apply certain stan-dard techniques in drawing these lines. A hidden edge line that is supposed to join a visible or another hidden line must actually contact the line, as shown in the upper views of figure 3-27;

Figure 3-25.-Use of visible edge lines.

Figure 3-26.-Use of hidden edge lines.

Figure 3-27.-Correct and incorrect procedures for drawing adjoining bidden lines.

the incorrect procedure is shown in the lower views.

Figure 3-28 shows an intersection between a hidden edge line and a visible edge line. Obviously, on the object itself the hidden edge line must be below the visible edge line. You indicate this face by drawing the hidden edge line as shown in the upper view of figure 3-28. If you drew it as indicated in the lower view, the hidden edge line would appear to be above, rather than beneath, the visible edge line.

Figure 3-29 shows an intersection between two hidden edge lines, one of which is beneath the other on the object itself. You indicate this fact by drawing the lines as indicated in the upper view of figure 3-29. If you drew them as indicated in the lower view, the wrong line would appear to be uppermost.