Tatting is a technique for handcrafting a particularly durable lace from a series of knots and loops. Tatting can be used to make lace edging as well as doilies, collars, accessories such as earrings and necklaces, and other decorative pieces. The lace is formed by a pattern of rings and chains formed from a series of cow hitch or half-hitch knots, called double stitches, over a core thread. Gaps can be left between the stitches to form picots, which are used for practical construction as well as decorative effect.