Lesson 12 of the Master Weaver series 'Problems in Teaching' on drafting block patterns. It explains how to derive one of the 64 variations of a three-block pattern directly from a profile, using the rules for two-block variations and the table of 64 variations, with a worked example (variation 4E) and treadling directions. It is preceded by a short practical project for a multicolour wool coat length, with a colour-striped warp, a four-shaft threading draft and treadling.