206 Exploring Drafting
Frontal
plane
Profile
plane
Horizontal
plane
First
angle
Fourth
angle
Third
angle
Second
angle
A
Third
angle
First
angle
B C
Figure 9-4 Third-angle and fi rst-angle projection. A—The principal planes used in orthographic projection
divide the drawing space into four quadrants. B—An imaginary box containing the object is placed in the third
quadrant for third-angle projection. C—An imaginary box containing the object is placed in the fi rst quadrant for
fi rst-angle projection.