In this section of the book Ching speaks about Masonry arches, lintels, wood joists floors, wood subfloors, wood plank, beam,steel open web joists, and reinforced concrete beams. Masonry arches utilize the compressive strength of brick and stone to span openings by transforming the vertical forces of a supported load into inclined components. A lintel is a structural horizontal block that spans the space or opening between two vertical supports. Wood joists floors are  an essential subsystem of wood light-frame construction. The dimension lumber used for joists is easily worked and can be quickly assembled on site with simple tools. Wood subflooring is the structural material that spans across floor joists, serves as a working platform during construction, and provides a base for the finish flooring. Wood plank-and-beam floor systems are typically used with a supporting grid of posts or columns to form a skeleton frame structure. Open-web joists are lightweight, shop-fabricated steel members having a trussed web. Lastly reinforced concrete beams are designed to act together with longitudinal and web reinforcement in resisting applied forces.