How to Crochet Two Pieces Together: 5 Seams and When to Use Each
Whipstitch, mattress stitch, slip stitch seam, single crochet seam and the flat join: how to work each, what it looks like, and which to use for amigurumi, garments, blankets and bags.
Pattern at a glance
US terms- Skill level
- Beginner
- Time
- 20 minutes
You'll need
- Two pieces to join
- Tapestry needle
- Hook
- Clips or stitch markers
In this post
To join two crochet pieces, either sew them with a tapestry needle (whipstitch or mattress stitch) or crochet them together with a hook (slip stitch or single crochet seam). Sewn seams are flatter and almost invisible; crocheted seams are faster and stronger. Pin the pieces together with clips first so the edges line up stitch for stitch.
The rest of this post is just below — free, as always.
Which seam to use
| Seam | Look | Best for |
|---|---|---|
| Whipstitch | Small diagonal stitches, slightly visible | Amigurumi parts, granny squares |
| Mattress stitch | Invisible from the front | Garments, side seams |
| Slip stitch seam | Firm, slight ridge on the back | Bags, baskets, sturdy joins |
| Single crochet seam | Raised decorative ridge (if worked on the front) | Blankets, cushions, bag sides |
| Flat slip stitch join | Flat, neat line | Granny square blankets |
How to work each seam
- Whipstitch: Hold the pieces right sides out. Insert the needle through both pieces from front to back, bring it over the top edge, and repeat in every stitch.
- Mattress stitch: Lay the pieces side by side, right sides up. Pass the needle under a post on the left piece, then under the matching post on the right piece. Zigzag up, and pull every few stitches — the seam closes invisibly.
- Slip stitch seam: Hold the pieces right sides together. Insert the hook through both edge stitches, pull up a loop and through the loop on the hook. Repeat.
- Single crochet seam: Hold the pieces wrong sides together for a ridge on the front (right sides together for a hidden ridge). Single crochet through both edge stitches.
- Flat join: Lay squares side by side, right sides up. Slip stitch through the back loops of the facing edge stitches, alternating sides.
Tips for neat seams
- Clip the pieces every inch or two so they don't shift.
- Use the same yarn as the pieces, or a contrast colour on purpose.
- Block pieces to the same size before joining — how to block crochet.
- For granny squares specifically, see how to join granny squares.
- Sewing on amigurumi parts? Leave a long tail when you fasten off.
Common questions
What is the strongest way to join crochet pieces?
A slip stitch or single crochet seam worked with a hook. They're more secure than sewn seams.
What is the most invisible crochet seam?
Mattress stitch. It pulls the edges together from the front so the seam disappears.
Should I join with right sides together or wrong sides together?
Right sides together hides the seam on the inside; wrong sides together shows it as a ridge on the outside.
Which seam is your go-to? 🪡
Stuck on a step? Crochet Help & Fixes answers the most common problems — curling, shrinking, wavy circles and more.
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