These locking stitch markers were designed to hook into the knitted or crocheted stitch within a row and will not slip out while you continue working. Use them to mark increases or decreases in your pattern... Or use them to mark a mistake that you need to rip back to or catch that dropped stitch before it runs down through what you have already knitted. Package comes with 20 pieces that will slide easily on needles up to US size 8 and a convenient storage pouch.