What is flatlock?
A flatlock seam joins two pieces edge to edge with a flat, ladder-like stitch so there is no ridge on the inside. It is used where the seam sits against skin during movement — leggings, sports bras, base layers — to prevent chafing.
Why it matters
It is the seam that separates activewear from a tee with stretch fabric. Buyers who train in the garment feel the difference in the first session.
On our floor
Flatlock on leggings, bras and fitted performance tees; overlock elsewhere for strength.
Common questions
- Flatlock or overlock?
- Flatlock against skin in activewear; overlock for everything else.
- Is flatlock less durable?
- Slightly, in pure strength; for its use — stretch garments against skin — it is the right seam.
- Can flatlock be a design feature?
- Yes — contrast-thread flatlock on the outside is a common activewear detail.
- Does it cost more?
- Marginally, in machine time. Specified per garment.
Related terms
overlock
An overlock — or serge — is a stitch that joins two pieces and wraps the raw edge in looped thread in a single pass, trimming as it goes.…
coverstitch
A coverstitch is the pair of parallel stitch lines you see on the outside of a t-shirt hem, cuff or neckband, with a looped thread covering…
polyester
Polyester is a synthetic fibre that wicks moisture, dries quickly, resists shrinking and holds colour through hot washing. It is the fibre…
cut and sew
Cut and sew means the garment is made from fabric — cut to a pattern and sewn — rather than bought as a finished blank and decorated. It is…
Where this applies
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