Drawing the section through points K and M on the lateral edges of the pyramid and a point L on a side of the base.

1. In the plane SAC , draw the line KL, the trace of the section in this plane.
2. Mark the intersection point P of KL and SC.
3. In the plane SBC, draw the trace PM of the section and mark its intersection point with BC.
4. Now we have all the four vertices of the section and can complete the construction.