So at last our journey is getting to the finishing stages: we have a yarn!  However, it is a single yarn: twisted in one direction only.  Single yarns alone are prone to kink or to make a garment or sock spiral if over-twisted, but if they are not twisted enough they fall apart.  So getting the correct twist is important for the end use as well as for the handle and balance of the yarn.  The key is both to have sufficient twist to hold the yarn together for its designed purpose and to have no more than sufficient twist in order to maintain softness, bulk and memory characteristics of the wool.