ISO 2 is an international standard for direction of twist designation for

yarn Yarn is a long continuous length of interlocked fibres, used in sewing, crocheting, knitting, weaving, embroidery, ropemaking, and the production of textiles. Thread is a type of yarn intended for sewing by hand or machine. Modern manu ...

s, complex yarns, slivers, slubbings, rovings, cordage, and related products. The standard uses capital letters S and Z to indicate the direction of twist, as suggested by the direction of slant of the central portions of these two letters. The handedness of the twist is the direction of the twists as they progress away from an observer. Thus Z-twist is said to be

right-handed In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more dextrous. The other hand, comparatively often the weaker, less dextrous or simply less subjecti ...

, and S-twist to be left-handed. The convention of using these two letters to unambiguously designate twist direction was already used in the cordage industry by 1957.

References

External links

ISO 2:1973
Textiles — Designation of the direction of twist in yarns and related products Yarn #00002 {{Standard-stub