What coverstitch means

Short answer: Coverlock is a seam with two or three parallel rows of stitching on the front and a covering thread on the back. It is used on edges that need to stretch with the body. Here is how it is built, where you find it and how to look after it.

What coverlock is

Coverlock is a seam type used on knitted fabric. On the front you see two or three parallel rows of stitches, and on the inside a covering thread runs across them. The seam is made to follow the fabric when it is stretched, and that is the whole point of it in everyday wear.

How it is sewn

The needles sew parallel rows through the fabric, and a looper on the machine lays a thread across them on the inside. That gives a seam with some flexibility of its own. It can be stretched without popping, and it lies flat against the fabric instead of forming a thick, stiff edge.

Why it is used on edges

The hem of a t-shirt is stretched every time you pull it on and off. The seam has to give and return without changing shape. An ordinary straight stitch would split, because the thread cannot stretch. See bamboo t-shirt for women if you want to look at the hems.

Where you find it

You find it on the bottom hem of t-shirts, on sleeve edges and in the waistbands of underwear. Anywhere the edge must stretch over a hip or a hand, you need a seam that goes along with it. See also bamboo polos for men and look for the seam along the edges.

How to recognise it

Turn the garment inside out and look at the edge. The front shows two parallel seams with a little space between them, and the inside has a flat thread that looks like a small net. That is the sign of coverlock. See bamboo jogging suit for men and try to find the seam yourself.

Coverlock or flatlock

Coverlock and flatlock look alike but do not do the same job. Flatlock joins two edges that are laid against each other to form a flat seam. Coverlock closes a single edge, usually one that is folded over. That is why it is used to finish a hem, not to join two pieces.

Why the seam pops

When a seam pops, it has usually been stretched hard without enough elasticity in the thread. It happens most often if you pull hard on an edge while dressing, or stretch it over something too narrow. Take hold of the fabric rather than the edge, and the seam will last longer.

How to repair it

If a seam has come undone, you can repair it at home. Sew over it with a zigzag stitch to keep the stretch, because a straight seam will split when the fabric is pulled. Use a needle made for knits and a thread in the same colour as the fabric. Sew close to the old seam.

Care in daily use

Wash the garment according to its care label, and avoid hanging heavy things from the edge, as the seam can be pulled out. Hang knitwear over a hanger at the shoulders so the edge does not carry the whole weight. An edge that is not overstretched keeps its shape for longer.

Frequently asked questions

Is coverlock the same as flatlock?

No. Flatlock joins two edges, coverlock closes a single edge. Both are seams for knits, but they are used for different things and look different on the front and the inside.

Why does the seam pop sometimes?

Under hard stretching, when the thread lacks enough elasticity. It usually happens if the edge is pulled hard, so it is better to take hold of the fabric, not the seam, when dressing.