Introduction

A straight line can be defined as the shortest distance between two points. The projection of these two points translates on to lines as well.
The position of a straight line is described with respect to the two reference planes. It may be:
1. Parallel to one or both the planes, as shown in Fig. 1.

Fig. 1 Line Parallel to both the planes.

2. Contained by one or both the planes, as shown in Fig. 2.

Fig. 2 Line inclined to HP and parallel to VP.

3. Perpendicular to one of the planes, as shown in Fig. 3.

Fig. 3 Line perpendicular to HP

4. Inclined to one plane and parallel to the other, as shown in Fig. 4.

Fig. 4 Line Parallel to HP inclined to VP

5. Inclined to both the planes, as shown in Fig. 5.

Fig. 5 Line inclined to both the planes