Crochet emerged as a distinct
textile art during the early 19th century, and many crochet hooks survive from that period. These early tools generally fall into two categories: thin steel hooks inserted into separate handles and single-piece hooks made from materials such as bone, wood, or metal. Although the distinction between steel and non-steel hooks persists, most modern hooks are manufactured as single pieces. A variety of coverings may be applied to the handle for ergonomic reasons. Ornate handles have also been added throughout time, with one method being
scrimshaw during 19th century Europe. Crochet hooks are currently produced in diameters ranging from 0.35 mm to 25 mm. These diameters are indicated both directly in millimeters and by various numerical or literal
gauge systems. Hooks under 2.0 mm are made of steel (for its strength) and are alternately termed steel-, lace- or thread hooks. Hooks of 2.00 mm or larger diameter are called yarn hooks or regular hooks. Aluminum is widely used between 2.0 mm and 6.0 mm because of its balance between strength and weight, while larger hooks are often made from bamboo, wood, or plastic. The indicated size boundaries between the types are, however, approximate. With the exception of the thinnest hooks, which are invariably made of steel, other materials may be encountered outside the indicated ranges. Historical materials for handles and some one-piece hooks include bone, porcupine quill, celluloid, agate, ivory, and fossilized mammoth ivory. Longer hooks are used in
Tunisian crochet to hold multiple live loops simultaneously. A form with hooks at both ends is also used for Tunisian and other types of crochet that cannot be made with the standard hook, such as
cro-hooking. == History ==