If twist is imparted to a fiber strand, it takes effect primarily where it encounters least resistance, i.e. in the thin places.
If a draft is now applied to the strand, the fibers begin to slide apart at the locations where the friction between them is least, i.e. where the twist is lowest. This is at the thick places. They are drawn first until they reach the volume of the thin places.
After that, the twist is distributed and the draft affects all portions uniformly. If another thin place were to arise, the whole procedure would be repeated. Compensation occurs continually. This operation is typical of selfactor spinning and woolen spinning systems.