The first part of a 1903 trade-journal article on the construction of leno cloths, written for textile designers. It explains the doup heddle, the doup shaft, and the ground and crossing threads, and defines the related terms. It then walks through the harness lifts for the plain pick and the crossing pick in the simplest leno, and describes the hemstitch leno, with two picks per shed. Figures 1-10 include doup diagrams and interlacement grids, and the article ends "to be continued."