For this reading, Ching once again goes into materials, but talks about what specific purpose each subcategory of material does, along with some general rules of thumb. For masonry arches and lintels, he explains how each structure is made, what its purpose is, how they differ from each other, and what general spans they come in. As for wooden joists, beams, subflooring, decking and planks, he tells us examples of how they are made, showed us the length of them, what each wooden structure means/represents, and tells us how to properly use each and every structure. Ching also goes back to the topic of steel, giving us a sense of how beams and open-web joists work. Open-web joists are joists that form a sort of “web” seen through sections. These webs help join together beams and other supports. Metal decking come in three forms, composite, form and cellular decking. Composite decking is used to balance tensions with concrete slabs that have a ribbed pattern. Form decking is used for formwork on reinforced concrete slabs. Cellular decking is done by welding a corrugated sheet on to a steel sheet, forming spaces for engineering/electrical work.