CO

To cast on (CO) is to create the initial loops on a knitting needle that form the foundation row of a knitted fabric. Without this first step, you have no base to build from. The cast-on loops must be secure enough to hold tension during the subsequent rows of knitting, yet loose enough to prevent excessive strain on the working yarn or the needle itself.

Multiple cast-on methods exist, each producing different edge characteristics and requiring different hand techniques. The long-tail cast-on uses a single length of yarn and creates a reversible, elastic edge suitable for most garments. The cable cast-on builds loops off a working yarn and produces a firm, slightly corded edge often used on cuffs or bind-offs. The provisional cast-on uses waste yarn and allows live stitches to be picked up later, common in seamless construction. The thumb cast-on requires minimal yarn and works quickly for small projects. Industrial flat-knitting machines typically use a comb-and-presser system to establish cast-on stitches mechanically across the needle bed.

The number of cast-on stitches directly determines the finished width of the piece. Miscounting at this stage compounds through the entire project. Tension during casting on affects how easily subsequent rows feed onto the needles and influences the overall fabric drape. Too-tight cast-ons restrict movement and can snap yarn; too-loose ones create laddering or uneven gauge in the first rows.

The term comes from the action of placing yarn onto the needle in a controlled manner. Different regional knitting traditions have developed distinct CO methods, and textile workers often develop strong preferences based on their training and the specific yarns and gauges they work with regularly.