The Short Answer:

Five stitch types cover almost every seam on a hoodie.

Lockstitch (ISO 301) for stable, non-stretch areas like labels and topstitching.

Overlock (ISO 504/514) to join and finish knit seams so they stretch without popping.

Coverstitch (ISO 406) for clean, flat hems and cuffs.

Flatlock (ISO 607), where seams sit against skin and bulk matters.

Bar tacks to reinforce stress points like pocket corners and drawcord exits.

If a tech pack or quote uses a term you can’t picture, find its chapter below.

Each one covers what the stitch is, where it belongs, and what to write in your spec.

Chapter 01

Know the Two Stitch Families Before You Read Another Tech Pack:

Every stitch on your hoodie descends from one of two families: lockstitch or chainstitch.

Learn the difference, and once and a half the jargon in your quotes stops being jargon.

ISO 301 · Lockstitch ISO 401 · Chainstitch ISO 101 · Single-thread chain

Lockstitch (ISO 301): two threads, locked in the middle

A lockstitch uses a needle thread on top and a bobbin thread underneath.

The machine loops them together inside the fabric, so the “lock” sits in the middle of the layers.

The result looks identical on both sides: a neat, straight line of stitches.

Its strengths: it is tight, secure, and hard to unravel.

Cut a lockstitch in the middle, and it holds on either side of the cut.

It also uses the least thread of any stitch type.

Its weakness: almost no stretch.

A lockstitch seam extends only as far as the thread itself gives, roughly the elasticity of the thread, not the fabric.

Put a plain lockstitch seam across a stretchy fleece panel, and the fabric stretches, the seam doesn’t, and the thread snaps.

That cracking sound when someone pulls a cheap hoodie over their head is usually a lockstitch used where it shouldn’t be.

On a hoodie, lockstitch belongs on stable, low-stretch work:

Attaching woven labels, topstitching a pocket opening, setting a zipper on wovens, and decorative straight stitching.

It is the default stitch on a home sewing machine, which is why founders recognize it and why factories have to talk them out of specifying it everywhere.

Chainstitch (ISO 401): loops that give

A chainstitch forms by looping threads through each other in a chain that runs along the underside of the seam.

No bobbin a looper mechanism feeds the underthread continuously, so the machine runs faster and longer without stopping to reload.

The loops are the point. Because each stitch is a loop rather than a lock, the seam extends with the fabric.

Chainstitch and its descendants are why knitwear seams survive being stretched.

The trade-off: pull the right thread at the end of a chain stitch, and the whole seam can unzip like a sack of rice.

Factories manage this with back-tacking, seam sequencing, and by never leaving a chain run-off exposed.

It also consumes more thread than a lockstitch, which is one reason thread consumption shows up as a real line in costing.

Why does the family matter more than the name?

Overlock, coverstitch, and flatlock the three stitches that dominate hoodie construction are all chainstitch descendants.

They inherit the stretch. Lockstitch stays in its lane: stability, precision, minimal bulk.

So when a quote lists stitch types, you are really reading a map of where the factory expects stretch and where it expects stability.

If the map looks wrong, lockstitch side seams on a stretch fleece, for example that is your cue to ask questions.

Your tech pack is where you set this in writing; if you haven’t built one yet, start with our tech pack guide and pull the stitch callouts from the chapters below.

From the Floor:

The most common correction we make to first-time tech packs is a spec that says “straight stitch all seams.” On a 320 GSM brushed fleece, that seam fails in wear-testing within days.

We flag it at pre-production review, swap the joins to a four-thread overlock, and keep lockstitch only for the topstitching.

Spec Takeaway:

Lockstitch for stability and looks. Chainstitch descendants for anything that stretches. If a seam crosses stretch fabric, its stitch must stretch too.

One more family member worth recognizing:

The single-thread chain stitch (ISO 101).

It unravels by design, which makes it the standard for basting and for temporary construction stitches.

If you see 101 on a spec sheet, it is scaffolding; it should not be holding anything together in the finished garment.

The same construction logic applies across every panel of the garment; our hoodie construction and panel guide walk through where each seam sits on the body.

Stitches vs. seams: reading both halves of the spec

One more vocabulary trap.

A stitch is the thread formation for everything this guide has covered so far.

A seam is how the fabric panels are arranged when that stitch joins them.

Tech packs spec both, and they use different code systems:

ISO 4915 for stitches and ISO 4916 for seam types.

Four seam types cover nearly everything on a hoodie:

  • Superimposed (SSa). Two panels stacked face to face, sewn near the edge. The default seam in all apparel, your side seams and sleeve seams, are superimposed seams joined by an overlock stitch.
  • Lapped (LSc). One panel overlaps the other, often with edges folded in and two rows of stitching the construction behind flat-felled seams on denim and heavy-duty work. On hoodies it appears where a panelled design wants visible, rugged seam lines.
  • Bound (BSa). A strip of fabric wraps a raw edge and is stitched through. Hood openings, necklines, and pocket mouths on premium builds are often bound by the fact that it costs more in material and labor and signals quality up close.
  • Flat / butted (FSa). Edges meet without overlapping the seam arrangement that flatseam stitching (Chapter 4) is built on.

Why this matters to you: when a quote line reads “SSa + 514,” the factory is telling you both the panel arrangement and the thread formation.

Read both halves, and the line stops being noise it becomes something you can approve, question, or change.

Chapter 02

Overlock: The Stitch That Keeps Knit Seams From Falling Apart

Overlock, also called serging, carries most of a hoodie’s seam strength.

It trims the raw edge, wraps it so the knit can’t unravel, and joins the two panels in a single pass, which is why it’s the default for fleece and French terry.

(For where that pass sits in the full build sequence, see how a hoodie is made.)

What that guide doesn’t tell you is which overlock to spec, and the thread count is the whole answer.

ISO 503 · 2-thread ISO 504 · 3-thread ISO 514 · 4-thread ISO 516 · 5-thread safety

Reading the thread count:

Overlock variants are named by thread count, and the count tells you what the stitch is for:

  • 2-thread (503): edge finishing only. It seals a raw edge but is not strong enough to be the seam itself. Common on hems before folding, or on lightweight layers.
  • 3-thread (504): light seaming and clean edge finishing. Fine for underwear and tees; on a heavy hoodie it is usually just the finishing stitch.
  • 4-thread (514): the hoodie standard. Two needle threads add a safety row, so the seam holds even if one thread breaks. This is what should be joining your side seams, sleeve seams, and raglan seams on mid-to-heavy fleece.
  • 5-thread safety stitch (516): an overlock plus a separate chainstitch row in one pass. The strongest common option standard on wovens and heavy-duty work, and worth specifying on heavyweight hoodies above: 400 GSM or anywhere a returns-driven brand wants maximum seam security.

What to check on a sample?

Stretch the seam gently along its length.

It should extend with the fabric and recover without a popped stitch.

Look at the wrapped edge: loops should be even and snug against the fabric, not loose, and not curling the edge.

A wavy, stretched-out overlock seam means the machine’s differential feed was set wrong for the fabric a fixable settings issue, but one you want fixed before bulk.

Spec Takeaway:

Write “4-thread overlock (ISO 514) on all joining seams” for a standard fleece hoodie.

Upgrade to 5-thread safety stitch (516) on heavyweights. 3-thread is finishing, not structure.

Chapter 03

Coverstitch: How Hems and Cuffs Get That Clean Twin-Needle Finish

Look at the bottom hem of a well-made hoodie from the outside: two parallel rows of straight stitching.

Flip it over: a flat grid of looper thread covering the raw edge.

That is coverstitch, and it is the difference between a retail finish and a homemade one.

ISO 406 · 2-needle ISO 605 · 3-needle

What coverstitch is for?

Coverstitch exists to finish hems on stretch fabric.

The fabric edge is folded up once, and the machine sews through both layers with two (or three) needles while a looper thread travels underneath, covering the raw edge and binding the fold flat.

Because the underside is a chain of loops, the hem stretches.

A lockstitch twin-needle hem looks similar from the outside but pops when the hem stretches, a classic sign of a corner cut in production.

The loops on the underside are how you tell them apart in ten seconds.

Where does it appear on a hoodie?

  • Bottom hems on styles without ribbed waistbands; the coverstitched hem is the standard finish.
  • Sleeve hems the same logic on cropped or rib-free sleeve designs.
  • Attaching a ribbing cover stitch over the join where cuffs and waistbands meet the body gives a flat, secured, retail-grade seam.
    Ribbing choice and coverstitch quality travel together; we cover the rib side of that decision in our cuffs, hems, and ribbing guide.
  • Neck tape and binding 3-needle coverstitch (605) frequently secures neck tape flat on premium builds.

2-needle vs. 3-needle:

2-needle (406) is the standard: two rows outside, loops inside.

3-needle (605) adds a center row for wider coverage and a stronger, more deliberate look that reads “performance” or “premium basics.”

It costs slightly more in thread and machine time.

Neither is better; they are different design statements.

Pick one and put it in the tech pack, because a factory left to choose will choose whatever its line is already set up for.

From the Floor:

On our finishing line, the most frequent coverstitch defect we catch at QC is skipped stitches, where the hem crosses a side seam four layers of fleece under the needle instead of two.

Our fix is slowing the machine at seam crossings and sizing the needle up for heavy GSM fabrics. Replace with a real floor detail and your actual needle sizing practice.

Spec Takeaway:

Spec “2-needle coverstitch (ISO 406) on hems and cuffs” as your baseline.

Check the underside of every sampled hem: loops mean stretch; a plain straight stitch means it will pop.

Chapter 04

Flatlock: The Seam You Spec When Comfort Is the Product

Every other seam in this guide has a ridge two-seam allowance pressed to one side, sitting between the garment and the skin.

Flatlock removes the ridge entirely. The two panels butt edge to edge, and the stitch bridges them flat.

ISO 607 · Flatseam. Also sold as: flatlock / flat seam / butt seam

Why does flat matter?

Seam allowance bulk is invisible until the garment moves.

Under a backpack strap, inside a base layer, on a sleeve seam during a workout, a raised seam is where chafing starts.

Flatseam construction (ISO 607) trims both edges, butts them together, and covers the join with a wide, stretchy stitch on both faces.

The seam ends up no thicker than the fabric itself.

The second benefit is stretch. Flatlock is among the stretchiest seam constructions available, which is why it dominates activewear, base layers, and performance knits.

The third is the look: the wide, ladder-like stitch reads as technical, and designers use it in contrast to thread as a visible design feature.

Where does it belong on a hoodie?

Flatlock is not a whole-garment default for standard fleece; a 4-thread overlock is faster, cheaper, and strong.

Flatlock earns its cost in specific placements:

  • Performance and athleisure hoodies with full flat-seam construction on lighter technical fleece and poly blends, where next-to-skin comfort is the selling point.
  • Raglan and shoulder seams under straps and against movement, even on otherwise standard builds.
  • Contrast-thread styling visible flatlock in a pop color as a deliberate design line.

The honest trade-offs:

Flatseaming needs a dedicated machine, more threads per seam, and tighter operator skill, but the butted edges leave no seam allowance to hide misalignment.

That shows up in cost: expect a per-unit uplift of $0.40-$0.90 for full flatseam construction versus standard overlock, depending on seam count.

It is also less forgiving on very heavy, unstable fleece; the construction shines on light-to-midweight technical knits.

Spec Takeaway:

Spec flatseam (ISO 607) by placement, not by default: shoulders and raglans for comfort, full-body only on performance styles that justify the cost.

Chapter 05

Bar-Tacks: Cheap Insurance at Every Stress Point

A bar-tack is a short, dense block of zigzag stitching, usually 6 to 13 millimeters of concentrated thread, sewn wherever force gathers on a garment.

It takes a machine two seconds.

It is the cheapest durability upgrade in apparel manufacturing.

Where does force gather on a hoodie?

  • Kangaroo pocket corners the highest-stress point on a pullover, and the one most guides already tell you to check. What they don’t give you is the spec: two tacks per corner pair, perpendicular to the pull.
  • Drawcord exits where the cord leaves the hood channel, every adjustment pulls on a few millimeters of fabric. Bar-tacks (or metal eyelets plus bar-tacks) keep the exit from elongating.
  • Zipper tops and bottoms on zip-ups: the end of the zipper tape takes the full opening force of every wear.
  • Vent and side-slit tops: any deliberate opening in a seam ends in a stress concentration. Tack it.
  • Belt loops and hardware anchors on utility and techwear builds; every strap anchor gets tacked.

What a good bar-tack looks like?

Dense, even, fully covering a solid block, not a sparse zigzag.

It should sit perpendicular to the direction of pull, catch all fabric layers, and back onto a stable structure (a seam allowance or interlined area), not open single-layer fabric, which a tack can tear through instead of protecting.

Count them on your sample.

A standard pullover should carry at least 6 bar-tacks: two per pocket corner pair and two at the drawcord exits, plus any style-specific points.

If your sample arrives without them, that is not a style choice; it is a cost cut, and it predicts how the factory treats every other invisible detail.

From the Floor:

We run bar-tacking as its own station at the end of assembly with a checklist per style pocket corners, drawcord exits, and zip stops because tacks skipped mid-line are the defect that only shows up after a month of wear, long past QC.

Spec Takeaway:

List every bar-tack location explicitly in the tech pack.

“Reinforce stress points” is not a spec; “bar-tack ×2 per pocket corner, ×2 drawcord exits” is.

Chapter 06

SPI and Thread: The Two Variables That Decide Seam Quality

Two hoodies can use identical stitch types and still be worlds apart in quality.

The gap hides in two numbers most founders never specify: stitches per inch and thread.

Stitches per inch (SPI):

SPI is stitch density, which is how many stitches the machine places in one inch of seam.

It is the quality dial on every stitch type in this guide.

Higher SPI means more thread sharing the load, so a stronger, more durable seam and a finer, more premium-looking stitch line.

But the ceiling is real:

Too many needle penetrations too close together perforate the fabric, and the seam can tear along the stitch line like a postage stamp.

Higher SPI also means slower sewing, which is why low SPI is one of the quietest cost cuts in the industry.

Working ranges for hoodie-weight knits:

Application Typical SPI What low SPI looks like
Overlock joining seams, fleece 08-10 Long, loose loops; seam grins open when stretched
Coverstitch hems 10-12 Coarse, widely spaced rows; homemade look
Lockstitch topstitching 10-14 Sparse, uneven stitch line on visible details
Flatseam construction 12-16 Gaps in coverage; edges peek through the stitch

Pull a hoodie you consider premium, lay a ruler on a seam, and count.

Then count the same seam on a budget blank.

The difference is usually visible without the ruler.

Thread: the material inside the seam

Thread choice runs on three axes:

  • Fabric. Spun polyester is the knitwear default: strong, colorfast, slightly givey, and economical. Core-spun (polyester core, cotton, or poly wrap) adds strength for stress seams and heavy fabrics. Textured poly loopers give overlock and coverstitch undersides their softness against skin.
  • Size. Thread thickness is specified in tex or ticket number. Heavier fabric takes heavier thread; a general-purpose spec for fleece garments sits around Tex 27-40, with heavier tex for topstitching where the stitch line is a visible design element.
  • Match to fabric. The thread should be marginally weaker than the fabric it joins. If a seam is overstressed, you want the thread to break, a repairable failure, rather than the fabric to tear, which is not.
 
Spec Takeaway:

Add one line to your tech pack per seam group: stitch type + SPI + thread spec.

Example: “Side seams: ISO 514, 9 SPI, Tex 30 spun poly.”

That single line moves you out of the “decides nothing, gets the default” category.

Chapter 07

Match the Stitch to the Fabric: The Decision Matrix

Everything above compresses into one working rule:

The seam must move the way the fabric moves and hold the way the placement demands.

Here is the matrix to check any tech pack against.

Placement Spec This Why
Side, sleeve & raglan joining seams (fleece / French terry) 4-thread overlock (ISO 514) Stretch and safety row; the knitwear structural standard.
Joining seams, heavyweight fleece 400+ GSM 5-thread safety stitch (ISO 516) Chainstitch row backs up the overlock on heavy loads.
Bottom & sleeve hems 2-needle coverstitch (ISO 406) Flat, stretchable, retail-grade hem finish.
Ribbing attachment (cuffs, waistband, collar) Overlock join and coverstitch topstitch. Stretch and join, secured flat where the rib meets the body.
Performance / next-to-skin seams Flatseam (ISO 607) Zero ridge, maximum stretch, no chafe.
Topstitching, labels, wovens & trims Lockstitch (ISO 301) Clean, stable, and identical on both sides.
Pocket corners, drawcord exits, zip ends, vents Bar-tack Concentrated reinforcement at stress points.
Basting / temporary construction only Single-thread chain (ISO 101) Removable by design, never structural.

Three questions that resolve any seam decision:

  1. Does the fabric stretch here? If yes, the stitch must stretch: overlock, coverstitch, or flatseam. Lockstitch is disqualified.
  2. Does skin touch this seam under pressure? If yes, shoulders under straps, the base layer fits flatseam and earns its cost.
  3. Does force concentrate here? If yes, openings, exits, and anchors add a bar tack. When in doubt, tack it.

Run those three questions down every seam line on your spec sheet, and you will catch the majority of construction problems before a sample is ever cut which is exactly when they are free to fix.

You Can Now Read the Stitch Lines on Any Quote:

Five stitch types, one density variable, and one thread spec.

That is the entire working vocabulary of hoodie seam construction, and now the terms on your tech packs and factory quotes map to physical things you can picture, check, and specify.

The practical next step:

Take your current spec sheet (or the last quote you received) and run each seam line through the three questions in Chapter 7.

Anywhere the stitch does not match the fabric’s movement or the placement’s stress, you have found either a future defect or a question worth asking your factory.

Frequently Asked Questions

Overlock joins two fabric panels while trimming and wrapping the raw edges; it is the structural seam inside the garment.

Coverstitch finishes a folded hem with parallel rows of stitching on the outside and covering loops on the inside.

In short: overlock builds the seams, and coverstitch finishes the hems and cuffs.

Write one line per seam group covering stitch type, stitch density (SPI), and thread.

For a standard fleece hoodie that reads: joining seams ISO 514 four-thread overlock, 8-10 SPI, spun polyester; hems and cuffs ISO 406 two-needle coverstitch; topstitching and labels ISO 301 lockstitch; plus bar-tacks called out by location.

Naming the SPI and ISO code is what stops the factory defaulting to whatever its line is already set for.

The stitch cannot extend as far as the fabric.

This usually means a lockstitch was used on stretch fabric, or the stitch density is too low for the seam to share the load.

The fix is a stretch-capable stitch overlock, coverstitch, or flatseam at an adequate SPI.

For performance styles and any seam that sits against skin under pressure, yes, it removes seam bulk and chafing entirely and stretches more than any common alternative.

For a standard streetwear fleece hoodie, a 4-thread overlock is strong, comfortable, and more economical, so flatseam is usually specified by placement rather than across the whole garment.

SPI is stitches per inch, the density of stitching along a seam.

Higher SPI generally means a stronger, finer-looking seam up to the point where excessive needle penetrations weaken the fabric.

It is one of the simplest quality variables to specify and to verify with a ruler on any sample.

A bar tack is a short, dense block of reinforcing stitches placed where force concentrates.

On a hoodie, that means both corners of the kangaroo pocket, the drawcord exits on the hood, the top and bottom of any zipper, and the ends of any vents or slits.

Each tack takes seconds to sew and prevents the most common wear-related failures.

From the HOODIE manual

This is one chapter of The Complete Hoodie Manufacturing Guides

These chapters cover taking a hoodie brand from idea to shipped units, costing, sourcing, tech packs, QC, freight, and launch comparisons. All written from the Sialkot factory floor of Gibben Clothing.

Open The Full Hoodie Guides

On the floor · Sialkot

Written by

Faizan Ahmad

Chief Apparel Technologist & Head of Manufacturing, Gibben Clothing · Sialkot, Pakistan

Faizan leads production at Gibben Clothing, a cut-and-sew streetwear manufacturer in Sialkot, with 8+ years turning raw yarn into retail-ready hoodies, tees, bottoms, jackets, tracksuits, and headwear. He doesn’t just write about clothing; he works the floor, so every guide here is grounded in real fabric behavior, QC standards, and production data from live runs.