This is a traditional granny square that I've seen several places. I've used it for a blanket and a bag. When someone asked me for the pattern, I searched the Internet, but I couldn't find it. So I wrote it down, and now share it with you too!
Suitable crochet hook
Depending on the yarn.
Worsted weight yarn - appr. 12 cm (4 3/4 inches)
Start with 6 ch, make a ring.
1st round: 4 ch, 5 dtr * 3 ch, 6 dtr * 3 times, 3 ch, 1 ss in the 4th of the 4 ch.
2nd round: 5 ch ** 5 dtr, but leave the last yoh each time, and then finish pulling the yarn through all. * 5 ch 1 ss in the loop, 5 ch ** - ** 3 times, 5 ch, 1 ss in the 2nd of 3 ch.
3rd round: Change colour. Start in the top of a dtr group: * (3 dtr, 1 ch, 3 dtr, 2 ch, 3 dtr, 1 ch, 3 dtr) in the 3 ch loop of 1st round, 1 ss in the top of the next dtr group. * 4 times.1 ss where you startet with this colour.
4th round. Change colour: 4 ch, 5 dtr in the same ss, *(6 dtr, 2 ch, 6 dtr) in the loop of 2 ch, 6 dtr in the top of the next dtr group * 3 times (6 dtr, 2 ch, 6 dtr) in the loop of 2 ch, finish with 1 ss in the 4th of 4 ch.
5th round.New colour: start in ss on round 4: 1 ch, 1 dc in each of the next 5 dtr, 1 tr in the ch-loop between the dtr groups on round 3. * 1 dc in each of the next 6 dtr, 3 dc in the corner loop, (1 dc in ieach of tthe next 6 dtr, 1 tr in the 1 ch loop between the dtr groups on round 3), twice * 3 times. 1 dc in each of the next 6 dtr, 1 tr in the ch loop between groups of dtr on round 3, 1 ss in the first ch.
6th round: 3 ch, 1 tr in each stitch, 3 tr in the middle stitch in each corner, finish with 1 ss in the 3rd of the first 3 ch. ( this is what it says in my pattern, I think I uset dc in stead of tr on this round.)