Warp knitting directs multiple yarns through guides to form parallel rows of loops linked in a zigzag arrangement. Woolmark describes stable structures that can be open or closed, along with tubular and three-dimensional products. The machinery can produce long runs of fabric and more specialised garment forms.

Illustrative image
Illustrative image.

That construction provides an identification clue beyond surface softness or fibre composition. Woolmark also notes that tubular seamless knitwear can still require seams during final assembly. A tube, a machine method and a completely finished seam-free garment are therefore related ideas rather than identical descriptions.