What is it?
A flatlock is sewn with a deliberately loose needle thread, so the seam can be pulled open until it lies completely flat.
When should you use it?
- Decorative seams with contrasting thread
- Flat seams on activewear and loungewear
- Joining fleece without bulk
- Creative topstitch-style details
What fabrics work well?
Many knits and fleece work well, as do stable wovens that do not fray heavily.
How many threads?
Usually two or three, depending on your machine.
What should the finished stitch look like?
Once pulled open, loops on one side and a “ladder” on the other, with the fabric edges meeting evenly in the middle.
Common problems
- Seam will not open flat — the needle thread may be too tight for flatlocking
- Uneven edges — sew with the fabric folded, trimming lightly
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