Making the squares is the fun part. Joining forty of them is where a lot of blankets stall. The method you pick changes how the finished piece looks and how long the job takes, so it's worth choosing deliberately rather than defaulting to whatever you did last time.
1. Whip stitch
Hold two squares right sides together, thread a tapestry needle, and sew through the back loops of both squares, one stitch at a time.
Looks like: almost nothing from the front. A small ridge on the wrong side.
Best for: blankets, and anything where you want the squares themselves to be the feature.
Watch out for: pulling too tight. The seam should have the same give as the squares, or the blanket won't lie flat.
2. Flat slip stitch join
Place squares wrong sides together and slip stitch through the back loops of both with a hook rather than a needle.
Looks like: a neat flat line, slightly more visible than whip stitch.
Best for: when you want the seam almost invisible but prefer working with a hook.
Watch out for: slip stitches tighten easily. Go up a hook size for the join if yours come out stiff.
3. Single crochet join
Hold the squares wrong sides together and single crochet through both, so the ridge sits proudly on the right side.
Looks like: a raised line between every square. Decorative and deliberate.
Best for: bags and baskets, because it adds real structure and stiffness to the seam.
Watch out for: it uses more yarn and adds width. If you're matching a stated finished size, account for it.
4. Join as you go
Instead of finishing each square separately, you join each one to its neighbours during its final round, slip stitching into the adjacent square as you work around.
Looks like: a flat, near-invisible seam.
Best for: anyone who hates sewing up, and large projects where the thought of joining fifty squares at the end is what's stopping you starting.
Watch out for: you need to plan your layout in advance, and changing your mind about colour placement halfway through means undoing real work.
The four things that actually decide how it looks
- Block first. Squares that are all the same size go together without easing or stretching. This matters more than which join you choose — see our guide to blocking crochet.
- Join every square the same way round. Pick a direction and stick to it. Squares joined in alternating directions produce seams that look subtly different across the piece and you'll never quite work out why.
- Count the stitches on each side. If one square has 17 stitches along an edge and its neighbour has 18, something will pucker. Fix it before joining, not after.
- Weave in the ends as you go. Nobody has ever enjoyed facing 200 loose ends at the end of a blanket. Do each square's ends when you finish it and the last stage is just joining.
Which one should you use?
For a soft blanket that drapes, whip stitch or join-as-you-go. For a bag that needs to hold its shape, single crochet. If you're undecided, make five squares and try each join on a pair — ten minutes of testing beats redoing a whole blanket.
Patterns to practise on: the Granny Square Tote Bag and Sunburst Granny Square Tote are small enough to finish quickly, and the Daisy Granny Square Hat only needs a handful of squares. For something bigger, there's the Daisy Granny Square Baby Blanket and the Fleur Granny Square Cardigan.