For prisms, there are 4 positions it  may be placed with its base on HP.These positions are illustrated in figure 11.

Figure 11. Projections of a triangular prism resting on its base on HP with different positions.

There are 4 positions  in which pyramids may be placed with its base on HP.  These positions are shown in figure 12.

Figure 12. Projections of a triangular Pyramid resting on its base on HP with different positions.