Styles and design · 8 October 2026 · 3 min read

Overlock vs interlock: how seam edges are finished

Overlock vs interlock explained: how the two stitches finish raw seam edges, what tailors mean by each word, and what a neat edge looks like inside a kameez.

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The difference in brief

Overlock and interlock both mean machine stitching that wraps thread round the cut edge of a seam so the fabric cannot fray. In most South Asian tailoring shops, overlock is the standard three-thread edge finish and interlock is a denser, firmer version made with four or five threads. The words are used loosely, so one shop’s interlock can be another shop’s overlock.

That is why it pays to know what a good edge looks like, and to describe the result you want, instead of trusting either word.

What an overlock stitch does

An overlocker, called a serger in North America, does two jobs in one pass. A small blade trims the edge of the fabric, and loops of thread are thrown over the fresh cut to hold every yarn in place. The basic version uses three threads: one needle and two loopers.

On a stitched suit, the seam itself is normally sewn on an ordinary straight-stitch machine. The overlocker only neatens the raw edges of the seam allowance, either each edge separately, so the seam can be pressed open, or both together, pressed to one side.

What tailors usually mean by interlock

When a tailor offers interlock, it usually means a wider, closer edge stitch with an extra line of stitching beside the wrap. A four-thread stitch adds a second needle. A five-thread stitch adds a separate chain stitch a short way in from the edge, and is sometimes called a safety stitch. Either way the edge is held twice, so it resists fraying and pulling apart better than the three-thread version.

Two other uses of the word cause confusion. Interlock is also the name of a smooth double-knit fabric used for T-shirts, which has nothing to do with seams. And some factories use it for other machines altogether. If interlock is offered as an upgrade, ask what will actually look different inside the garment.

What a neat edge looks like inside a kameez

Turn a kameez inside out and look along the side seams. Good finishing is easy to recognise.

The thread covers the edge completely, with no whiskers of fabric poking through.
The loops lie flat and even. Loose loops catch on rings and bangles; loops pulled too tight make the edge curl or pucker.
The band of stitching is the same width from armhole to hem.
The thread is close to the fabric colour, so it does not shadow through pale cloth.
Thread ends are secured, not left as tails.
Some seam allowance remains beside the stitching. An edge trimmed right up to the seam leaves nothing to release, as our guide to letting out a kameez shows.

When plain overlocking is enough

For closely woven cottons such as lawn, cambric and khaddar, a tidy three-thread overlock is all a seam needs. The same goes for anything fully lined, because the lining covers the seams and takes the rubbing.

It is worth asking for more in three cases.

Fabrics that shed threads: raw silk, loosely woven jacquard and some linens fray fast, and a denser stitch or a bound edge holds them better.
Sheer fabrics: any overlocking shows through chiffon and organza. An enclosed seam is the better finish there; see what a French seam is.
Seams under strain: the seat seam of fitted trousers works harder than a kameez side seam.
With custom stitching, put the finish you would like in your notes when you ask for a quote. It is a request, and the written quote says what can be done on your fabric and design.

Common questions

Is overlocking the same as serging?

Yes. Serger is the North American name for the machine that British and South Asian sewers call an overlocker, and the stitch is the same.

Does overlocking hold a seam together on its own?

A three-thread overlock is an edge finish, so on woven clothes the seam is sewn separately with a straight stitch. Four and five-thread stitches can join and finish in a single pass, which is common in factory-made clothing and in knitwear.

Should I ask for interlock on every outfit?

No. On firm cottons a clean overlock does the job, and extra thread only adds bulk, which can show as a ridge on fine fabric. Keep the request for cloth that frays quickly or seams that take strain, and say what you want the edge to look like.

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