This lecture covers the concept of surfaces with constant null curvature, focusing on their development and properties. It explains how these surfaces can be easily manufactured by cutting them flat and discusses the construction of networks of curves in hyperbolic paraboloids. The presentation also delves into the rules between two lines, specifically parabolas and hyperbolas, within the parabolic hyperboloid. The instructor demonstrates the projection of these curves onto a normal plane and the determination of critical points. The lecture concludes with an exercise on deepening the understanding of these concepts.