Common crochet abbreviations include shortening stitch names to two letters, such as "sc," "dc" and "tr" for single crochet, double crochet and triple crochet stitches, respectively. Many patterns explain the abbreviations they contain in a small introductory section or in the beginning or end of a book of crochet patterns.
The abbreviation "sl st" is a common stand-in for slip stitch. The slip stitch is a useful stitch required to crochet designs on the surface of things or form a ring. Another type of shorthand that appears in crochet patterns is a set of instructions between parentheses or straight brackets. The steps inside these symbols should be repeated as many times as the pattern specifies.