Lesson 3 of Posselt's textile school series, on satin weaves as the third of the foundation weaves. It explains how satins differ from twills, gives the rule for constructing them with a counter number, and works through the 5-harness satin in full, showing the four counting-off variants and why they yield only one weave. It then covers the 6-harness irregular satin (large crow foot twill) and the 7-, 8-, 10- and 12-harness satins, with drawdown figures and a set of review questions.