Using mattress stitch to join your crochet pieces together will give you a secure, nearly hidden join. You can use both loops or just the back loops – I’ve used just the back loops here – or for a more invisible mattress stitch, use the same technique but first bring the yarn down at the stitch before (see box 22, below):
1. Place your squares in the order you want to sew them together and cut a piece of yarn about 3 times the length

2. Thread your yarn needle and bring it up in the very end stitch on the right (on this square that’s the corner chain closest to the stitches)

3. Pull through, leaving a tail – you’ll be grabbing the back loop from back to front

4. Bring the needle up in the corresponding stitch on the square above and pull through, grabbing the back loop

5. Repeat this again for the first and last stitches to secure the ends (back to front in the back loop of the white chain, back to front in the back loop of the pink chain)

6. Insert the needle into the back loop of the next stitch (on the bottom square)

7. Pull through

8. Insert the needle into the corresponding stitch on the square above, back to front in the back loop only

9. Pull through

10. Continue going along from back to front in the back loop of the bottom square…

11. Then back to front in the back loop of the top square…

12. Every inch or so…

13. Gently pull the yarn tight

14. Bringing the stitches together and hiding the yarn

15. Continue all along

16. Back view

17. When you get to the corner, do the same in the last stitch (in this square it’s the chain); back to front in the back loop only of the bottom square

18. Then back to front in the back loop only of the top square

19. Continue on to the next square, starting with the chain on the left, bottom…

20. Then top

21. This stitch is pretty good at hiding the joining yarn, but it works better if the squares are all the same colour

22. For this last square I’ve used a more invisible mattress stitch; use the same technique as above but first bring the yarn down at the stitch before: insert the needle into the stitch before, from the top (this is the same stitch the yarn is coming out of)…

23. Bring it out in the next stitch, back to front, back loop only

24. Front to back in the top stitch (where the yarn is coming out of)

25. Back to front in the next stitch, back loop only

26. This method is a little more difficult…

27. Until you get used to it

28. When you’ve done a few stitches…

29. Pull the yarn tight

30. You can’t see the joining yarn at all – you can see the difference between the two methods below

31. Back view

