Third article in Ralph Griswold's series on using L-Systems (string rewriting systems) in weave design. It shows how rules operating on shaft and treadle numbers can generate threading and treadling sequences (t-sequences) that grow more intricate with each generation. An example L-System with eight rules and a 15-digit seed is given, with a partial draft and drawdown of a crackle weave, and a second crackle example on the last page. It also notes how to handle shaft numbers above 9 and previews later articles.