crochet to look like knit one, purl one.

To crochet a scarf to look like a knitted rib, have your friend make a chain the desired length of scarf (note crochet will be worked end to end instead of side to side). Row 1: make slip stitch in second chain from hook, slip stitch in each chain across. Row 2: Ch 1 turn. Slip stitch in the back loop only of each slip stitch of previous row. Repeat Row 2 until scarf is desired width. End off. Finish ends.

Option 2: You can single crochet in back loop only instead of slip stitch. This will produce a ribbing (quicker too), but he appearance will not look as much like a knit one purl one ribbing as the slip stitch.

Hope this helps.