Pick up stitches are strands of yarn that have already been knitted in a garment or other project. A knitting pattern may instruct something like "pick up and knit 40 stitches," which means that the knitter is to first insert one needle into the specified number of yarn strands on an already knitted edge. Once these strands are placed, or "picked up" onto one needle, the other can be used to knit the 40 stitches. Picking up stitches on a finished edge and knitting another section may also be done in creative, experimental knit projects, often to get a change in stitch direction and/or color.
For instance, a one-piece patchwork style of placemat, table runner, pillow cover or blanket throw can be created by knitting a square, then picking up stitches from one of its sides. Depending on the chosen side for the pick up stitches, the stitch direction may change or stay the same. If the knitter desires, a totally different pattern as well as color and direction may be used for the next square made from the picked up stitches.
A knitted edge in which to pick up new stitches may be straight or may not be, such as in the case of underarm shaping in a sweater. The main reason pick up stitches are used is when a new addition to the knitted project is needed such as a sleeve to the shoulder edge. Since a knitted sweater sleeve is usually tapered in shape, a decrease method of knitting pick up stitches is often used. Every stitch on the shoulder's edge may be picked up and knitted, but the sweater pattern may then instruct for regular decreases, such as by knitting two stitches together, so that the sleeve will taper down to fit the wrist.
Evenly picking up the knitted stitches is necessary for a smooth look. When a knitted edge is already finished, or bound off, a technique of wrapping yarn around the needle when picking up and knitting the new stitches may be used to avoid leaving holes in the work. The pattern instructions for picking up stitches is sometimes abbreviated as "PU."
Pick up stitches are typically done to expand the knitted work. These kind of stitches take practice in order to get an even smoothness. Beginning knitters are advised to avoid patterns in which picking up stitches is necessary until they are more experienced in producing a uniform tension.