What flatlock means
Short answer: Flatlock is a seam in which two pieces of fabric are laid edge to edge and joined with a flat seam. No edge sticks up against the skin. Here we explain how it is sewn, why it is used and where you find it.
What flatlock is
Flatlock is a particular seam used in clothes where comfort matters. Two pieces of fabric are laid edge to edge and joined so that the seam lies flat instead of forming a ridge. You see it mostly in close-fitting clothes that you wear for many hours at a stretch.
How it is sewn
The fabric edges meet without overlapping, and the threads bind them together on both sides of the seam. That is the difference from an ordinary seam, in which two layers of fabric lie on top of each other and form a ridge. The result is a seam that lies level with the fabric, with nothing rising up.
A seam you barely feel
The seam can only be felt as a slight unevenness when you run a finger across it. It lies level with the fabric and forms no ridge pressing on the skin. That is the idea behind it: you should be able to forget there is a seam at all when you wear the garment.
Why it is used
Flatlock is used in garments that lie directly on the skin for many hours. An ordinary seam would rub there, and over a whole day that can leave a red mark or an uncomfortable feeling. The flat seam reduces that problem and makes the garment more comfortable from morning to evening.
Rubbing over a whole day
It is not the first minutes that are the problem, but the hours. An ordinary seam that rubs a little can seem harmless at first, but over a whole day you feel it. Where clothing moves with the body in particular, a flat seam is an advantage. See bamboo jogging suit for men.
Where you find it
Flatlock is found in underwear, sportswear and better nightwear. These are all garments where the fabric lies close to the body and comfort matters more than fast production. If you have a favourite garment you forget you are wearing, there is a good chance the seams are flat. See bamboo panties.
How to spot it from outside
From outside you can spot flatlock as two parallel lines of stitching with a flat zigzag between them. That is a good sign if you want to check whether a garment has this type of seam. Look at the seam on the inside of sleeves or sides, where it often sits, and notice how flat it lies.
Strength compared with overlock
Flatlock is flatter than overlock, but that does not mean stronger or weaker. The strength of the seam depends on the yarn and the machine, and a good flatlock can be as durable as other seams. What matters is that it is flatter and so rubs less against the skin.
Why it is not used everywhere
Flatlock is slower to sew than an ordinary seam and so costs more to make. That is why it is not found in every garment, only where the gain in comfort is greatest. See bamboo sleepwear for women for an example of clothing in which comfort is the focus.
Frequently asked questions
Can you see flatlock from outside
Yes, it shows as two parallel lines of stitching with a flat zigzag between. The seam lies flat against the fabric, and you feel it as a slight unevenness if you run a finger over it.
Is flatlock stronger than overlock
It is flatter, which is not the same as stronger. Strength depends on the yarn and the machine, and both seam types can be durable if they are sewn properly.
Why is it not used everywhere
It is slower to sew and therefore dearer. That is why it is used mainly in garments that lie close to the skin, where a flat seam makes the biggest difference to comfort.
You can find the full range at Bamboo-Clothing.com.
