ISO 16322-2:2005 specifies three procedures (diagonal marking, inverted-T marking and mock-garment marking) to measure the spirality or torque of woven and knitted fabrics after laundering.
The results obtained from different procedures may not be comparable.
ISO 16322-2:2005 is not intended to measure the spirality of fabrics as manufactured, but rather the spirality after laundering.
Note that some fabric constructions, such as denim, can have spirality intentionally introduced during manufacturing. Fabrics made on circular knitting machines can have inherent nonverticality of wale alignment.