A crochet hook is a type of needle, usually with a hook at one end, used to draw thread through knotted loops. Only one crochet hook is needed to make crochet stitches. A type of crochet needle with a hook at each end, known as a Cro-Hook, is used to make double-sided crochet pieces. The crochet hook's earliest use appears to have been in the late 1700s or early 1800s.
Hooks come in various sizes (measured in millimetres or fractions of an inch), according to the thickness of the needle. The size of the hook is usually matched with an appropriate ply or thickness of thread.
Hooks can be made of wood, plastic or metal and have been made with decorative handles. Some hooks are made with wooden or plastic handles with the hook made of metal and inserted into the handle.