Seam types in underwear from overlock to flatlock
Short answer: The two most common seams in underwear are overlock and flatlock. Overlock finishes the edge of the fabric and is stretchy, while flatlock lays the edges flat so the seam is smooth against the skin. Here we explain the difference and what to look for.
Overlock seams in underwear and what they are
An overlock seam is sewn over the edge of the fabric and finishes it so it does not fray. It is used a lot in knitwear because the thread gives when the fabric is stretched. You recognise it by the small loops along the edge. It is very common in underwear and T-shirts, and it gives a neat, solid result.
Flatlock and the flat seams
A flatlock seam places two pieces of fabric edge to edge and sews them together so the seam is flat. It can stick out less against the skin than an overlock seam. Many choose it when they want to reduce rubbing. You recognise it by a flat, wide seam that often looks like small ladders on one side.
Why the seam can matter
Underwear sits close to the skin, so a thick or rough seam can be felt, especially where the fabric rubs. That is why many look at where the seams sit. A flat seam seldom leaves a visible line under clothes. But the experience is personal, and a good overlock can also feel perfectly fine.
Where the seams sit
Look at where the seams lie: at the legs, waist, gusset and sides. Seams in the side panel can rub against the hip, and seams in the gusset are felt the most. Some brands move the seams to reduce rubbing, others use seamless knit. Read the description and look at the pictures of the piece. Also look at bamboo underwear for women.
Seamless knit as an alternative
Seamless underwear is knitted in one piece without the classic side seams. It can mean fewer seams, but has its own traits: it may fit closer and have thicker zones. It does not suit everyone. Try it if you want to see whether you like it. There is no right or wrong answer.
The quality of the seam
Good seams are even, without loose threads, and they give when you stretch them gently. Check that the seam does not split when you turn the piece. If the thread snaps when you stretch it, the seam probably will not last long. Quality shows in the detail, and you can check it yourself when the goods arrive.
Looking after seams
Wash underwear inside out in a laundry bag at a gentle temperature. That way the seams rub less against other clothes and last longer. Avoid the tumble dryer, because it can wear thread and fabric. Let the pieces air dry. The same goes for socks, and here you can look at all bamboo socks for women.
How to choose
Choose by what feels good for your body. Try different seams and notice how they feel after a whole day. If you are unsure, start with a single piece, for example a bamboo T-shirt for women, and notice how it feels. Your experience is the most important thing, not the name of the seam.
Frequently asked questions
What is the difference between overlock and flatlock?
Overlock is sewn over the edge of the fabric and finishes it, while flatlock places the edges flat against each other. Flatlock often gives a smoother seam against the skin.
Are flat seams always better?
Not always. Many find flat seams rub less, but the experience is personal, and a good overlock seam can feel fine too.
How do I look after seams in underwear?
Wash inside out in a laundry bag at a gentle temperature, avoid the tumble dryer and let the pieces air dry. That way the seams last better.
