Accurate knitting needle and crochet hook sizing is important for both crafts. The size of a crochet hook is determined by the diameter of its shaft. The cro-tatting tool is a tatting needle with a crochet hook at the end. One can also cro-tat with a bullion crochet hook or a very straight crochet hook. Also, instead of knitting needles, a crochet hook is used. The cro-hook, is a special double-ended crochet hook used to make double-sided crochet.