Corrugated Rib

Corrugated rib is the two-colour rib that finishes the cuffs, hems, and brims of stranded colourwork so the edges match the pattern above them. You knit the knit columns in one colour and purl the purl columns in another, carrying both yarns across the back as in any stranded knitting, which stripes the rib vertically in two colours. The catch, and the thing to know before using it, is that carrying the floats behind the rib robs it of the elasticity a normal rib has, so corrugated rib is firm and barely stretchy and should not be relied on to hug a wrist or draw in a hem the way plain rib does. Knitters often work it on a smaller needle or add a round of plain rib for grip. It is intermediate mainly because it is your first taste of managing two yarns in a rib and keeping the floats even. Kept relaxed, it makes a crisp, colourful, professional edge.