The overlock seam and where it belongs

Short answer: An overlock closes the fabric edge and can stretch. It is the standard seam in knitted clothing and should look even on the inside.

What it does

The overlock sews and finishes the edge in one movement. It closes the fabric edge so it does not fray, and it carries enough thread to stretch with the fabric. Without it a knitted fabric would roll up and come apart at the edge.

Where it is used

In side seams, armholes and crotch on almost all knitted clothing. It is not entirely flat, so in underwear it is often combined with a flat seam where the fabric lies against the skin. See bamboo t-shirts for men.

How to judge it

Turn the garment over. The thread should sit close and even with no gaps, and the edge should be fully covered. Uneven thread and visible fabric between the stitches mean hurried sewing. See bamboo clothing for women and bamboo underwear for men.

Frequently asked questions

Can an overlock come undone

Yes, if a thread breaks it can run. Tie off a loose thread end when you see one.

Is overlock worse than flatlock

No, it is stronger. Flatlock is flatter. They are used in different places.

Why are there four threads

Four threads give both a seam and an edge finish at once. Three threads are weaker.