The simple CROCHET Hook (above, lower) is used to crochet lace-style edgings, trims, buttons and garments as well as a variety of craft items. BUT some other useful 'hooks' (somewhat difficult to locate these days) can also be used for other crochet-based stitches.
HAIRPIN and TUNISIAN CROCHET
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Hairpin Crochet: A Hairpin hook (also used for Knotting or Netting) is used together with a basic crochet or Tunisian hook). A working thread is wound over and round the 'hook arms' to form a series of loops. These are then joined together with a simple crochet slip-stitch to form a continuous looping-style lace. This lace is gradually worked along the central posts and by using the end-bar to hold in place, a long length of 'lace' can be easily made to create fabulous trims, braids, garments or other decorative items.
Tunisian or Afghan Crochet: A Tunisian hook is very similar in appearance and length to a knitting needle except that instead of a point at the end, there is a hook. At the opposite end is a 'knob' like a knitting needle and this prevents stitches falling off. Unlike crochet which has only 1 (or just a few) loop on the hook and is worked 1-row at a time, Tunisian crochet is a 2-row procedure. Simply: row 1 is formed by 'picking up' stitches (like in knitting) - row 2 is made by working back along the row in pairs of stitches, pulling one stitch through another. It is almost a 'cross' between crochet and knitting - ideal for anyone who finds it difficult to crochet (especially if they have a knitting background) or a person who justs wants to enhance their crochet techniques. It produces a textile that is firm and hard-wearing so is suitable for furnishings and similar items as well as practical 'hard-wearing' garments. It's easy to make and its appearance is not unsimilar to a type of rib.
A very good reference book is a 1973 publication: Joan Fisher's Guide to Crochet.