The next round uses long single crochet stitches (long sc). Here's a link with closeup photos and details about long sc: http://crochet.about.com/library/weekly/aa042598.htm
Granny Square Rnd 3: Attach Color C in any corner ch-2 loop, (sc, ch 2, sc) in same corner loop, * sc in ea of next 2 sc, long sc in the rnd-1 dc that is directly below the next sc of this round (refer to photo to see the placement of the long sc), sc in ea of next 2 sc, (sc, ch 2, sc) in next ch-2 corner loop **, repeat directions between * and ** twice more, then sc in ea of next 2 sc, long sc in the rnd-1 dc that is directly below the next sc of this round, sc in ea of next 2 sc, sl st in top of beginning sc of this round. End off color C.
