The method of constructing an isometric drawing of an object
composed partly of inclined surface (and oblique edges) is
shown in figure 5.20 .Notice that inclined surfaces are
located by offset measurements along isometric lines.
Figure 5.20 Isometric drawing of normal surfaces
For example, dimensions E and F are setoff to locate the
inclined surface M, and dimensions A and B are used to
locate surface N.