B. VERTICAL PLANES
Vertical planes are perpendicular to the horizontal projection
plane. The horizontal view of all vertical planes shows the
plane as an edge view. The following figures show the three
basic positions for a vertical plane.
Figure 7.20 Vertical PlanesC. OBLIQUE AND INCLINED PLANES
The classification of planes is determined by their relationship
to the three principal projection planes: frontal, horizontal, and
profile. Principal planes appear as a true size in one of the
three principal projections and as edges in the other two.
Oblique planes and inclined planes do not appear true size in
any of the three principal views. Oblique and inclined planes
are not vertical or horizontal (level), and will not be parallel to
a principal projection plane.
♦ Oblique plane: An oblique plane is inclined to all
three principal projection planes, which results in each
view being foreshortened (distorted). The true size of