78 Chapter 5
Third-Angle Projection.
In third-angle projection the left view is placed on the left and the top view is placed on the top (Figure
5.7 B and C). This type of projection is primarily used in the United States and Canada. It should be noted
that not all views are necessarily used, and determination of which surface constitutes the front, back,
top, and bottom varies depending on the projection used.
In third-angle projection, the object lies below and behind the viewing planes. The planes are trans-
parent, and each view is pulled onto the plane closest to it. Using the six-sided viewing box, each view
of the object is projected opposite to the direction of sight onto the exterior walls of the box; that is, each
view of the object is drawn on the same side of the box. The box is then unfolded to view all of its exte-
rior walls, as shown in Figure 5.7C.
Figure 5.6 A multiview projection for a simple house. This is the format most used by architects and
engineers.