Take a look at any of your ready-to-wear knits and you may notice something about the hems, cuffs, and other edges. They don’t have the sorts of cast-on edges that you normally see in handknit pieces. While there are exceptions, most hems are either a band of knit fabric (ribbed or jersey) folded in half and sewn on, or…what? How do you even describe what’s happening on the cuffs of those socks and the hems of those sleeves? When you follow the stitches from the right side of the fabric to the edge to the wrong side, there is no apparent beginning or end, just stitches flowing from the right side to the wrong side, yet the fabric is a single layer. The edge is somehow both sturdy and flexible, keeping the edge neat and flat.

This is the magic of a tubular cast-on.