Twill

Twill's diagonal rib comes from a weave that offsets each pass by one or two threads, so the fabric shows a visible diagonal line running across the surface instead of the flat checkerboard of a plain weave. Most apparel versions run 2x1 or 3x1 construction, and the tight, offset structure makes the cloth more durable and more dimensionally stable than a plain weave of the same weight.

Six-panel structured caps — Richardson 112s, New Era 59FIFTYs — are almost always cut from twill because of that stability, and work shirts and chino-style pants lean on the same weave for abrasion resistance. Varsity jacket letters get cut from it for the same reason: the weave holds a clean edge when appliquéd and won't fray under a satin-stitch border.

Because it doesn't stretch or distort under stitch density, twill is the default ground fabric for embroidery — digitizers can push a denser fill stitch into it without the fabric puckering the way a loose knit would. Caps are embroidered rather than printed almost across the board, since the curved-panel construction and diagonal texture don't hold screen print detail the way a flat surface does.

Twill and canvas get lumped together in buyer requests for a 'heavy-duty' fabric, but the weave is the tell: one runs its rib at a diagonal you can trace with a finger, while the other lies in a flat, square plain weave with no diagonal at all. Confuse the two on a spec and you'll get the wrong hand, the wrong drape, and — on a cap especially — the wrong construction entirely.