Stitches and seams: how a garment is actually held together
A garment lives or dies at its seams. Two factories can use the same fabric and pattern and turn out very different shirts — the difference is which stitches hold them together and how. Here's the vocabulary, so you can read (and write) construction with confidence.
Stitch versus seam — two different things
People use the words interchangeably, but they aren't the same. A stitch is the way thread interlaces through the cloth — the machine's job. A seam is how two or more pieces of fabric are positioned and joined — the engineering of the join. One seam can be built with several stitch types. Get both right on your tech pack and there's no room for the factory to guess.
The core stitch types
Almost every operation on the floor is one of these. Each is identified by an international stitch-class number you can put straight on a spec.
Two threads locking in the middle of the cloth. Strong, neat, identical both sides — the workhorse for seaming and topstitching wovens. Doesn't stretch, so it's wrong for knits.
A looped chain on the underside. Slightly elastic and fast — used for long seams, denim inseams, waistbands and basting. Unravels if the chain end isn't secured.
Wraps the raw edge with thread as it trims it, stopping fray. Stretches a little, so it both seams knits and finishes the inside edges of wovens. The 516 "safety stitch" adds a chainstitch row for strength.
Parallel rows on top, a covering loop beneath. Stretchy and flat — the standard hem for knit tees and the neat double row you see on activewear.
Butts two edges together with no overlap, leaving a flat, bulk-free join that lies smooth against skin. The chafe-free seam on sportswear and base layers.
A dense, short zigzag that locks down high-stress points — pocket corners, belt loops, fly bases, the ends of a slit. Small, but the first thing to fail if it's missing.
Three more you'll meet by name: the blind hem (103) catches only a thread or two of the face so the hem is invisible from outside; the buttonhole and button-sew run on dedicated machines; and the simple zigzag (304) stretches, so it edges elastic and stretch trims.
Specify the stitch class and the seam class together. "Single-needle lockstitch, felled side seam" leaves nothing to interpretation.
The seams those stitches build
A handful of seam constructions cover most garments. They trade off strength, bulk, cost and how the inside looks.
| Seam | How it's built | Where it's used |
|---|---|---|
| Plain (superimposed) | Two faces together, one row of lockstitch, edges then overlocked. | The default seam almost everywhere. |
| Flat-felled (lapped) | Edges folded into each other and topstitched twice — fully enclosed, no raw edge. | Jeans, casual shirts, anywhere strength and a clean inside matter. |
| French seam | Sewn wrong-then-right side to bury the raw edges inside the seam. | Fine blouses, sheer and unlined fabrics. |
| Bound seam | A strip of binding wrapped over the raw edge and stitched. | Unlined jackets, necklines, a tidy visible finish. |
| Blind hem | Folded and caught with a 103 blind stitch. | Trousers, dresses, formal hems. |
Stitch density matters too
How many stitches sit in an inch — SPI — changes both look and strength. Too few and a seam gaps and pulls; too many and lightweight cloth puckers and the needle weakens the fabric. It's a real spec, not a detail, and worth its own conversation when you develop a style.
What to put on your tech pack
For clean, repeatable construction, state four things at every seam: the stitch class, the seam class, the SPI, and the thread. Mark where bartacks go. With those locked, sampling matches bulk, and quality doesn't drift between the sealed sample and the production run.
Send us your tech pack — we'll spec the right stitch at every seam.
Our team in Salem builds shirts, bottoms and dresses across single-needle, overlock, flatlock and bartack operations, and will recommend the construction your style and price point need.
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