If a pattern features rib at a cuff or a welt, chances are it's to give elasticity and snugness. It would be a pity to take away some of that stretchiness when you cast off, so a very common instruction is to "cast off in pattern".

What does it mean to bind off stitches in pattern in knitting?

Hi Linda – yes, “binding-off in pattern” means to knit the knits and purl the purls (as you have done in the ribbing up to that point), then binding off as you go. In other words, work a normal rib row, but every time you have two stitches on the right needle, bind one off over the other.

What does it mean to cast off in Rib?

Binding off in pattern is a technique that's often used when you're binding off rib stitch. Unlike a regular bind off, where you knit all the stitches on the bind off row, binding off in pattern requires that you knit the bind off row as if you were working the next row of your stitch pattern.