The grain is created in a woven fabric by the threads that travel
lengthwise and crosswise. The lengthwise grain runs parallel to the
selvedges; the crosswise grain should always be perpendicular to the
lengthwise threads. If the grains aren't completely straight and
perpendicular, grasp the fabric at diagonally opposite corners and pull
gently to restore the grain. In knit fabrics, the lengthwise grain runs
along the wales (ribs), parallel to the selvedges, with the crosswise
grain running along the courses (perpendicular to the wales).