Seam and stitch types: a plain guide for tech packs
The common stitch types (301, 401, 504, 514, 605, 607), where each is used on T-shirts, hoodies and woven garments, and how to write them in construction notes.
Updated 1 October 2026 · By Hem Apparel
Construction notes tell a factory how to sew each part of the garment. Most of it comes down to naming a stitch type and a seam finish for each area. Stitch types follow an international numbering system (ISO 4915), so a factory anywhere will recognise the numbers.
Common stitch types
| Stitch | Name | Typical use |
|---|---|---|
| 301 | Lockstitch | Woven seams, topstitching, labels, pockets |
| 401 | Double chainstitch | Stretch-free seams on jeans and workwear, strong and flexible |
| 504 | 3-thread overlock | Edge finishing and seaming on light knits |
| 514 | 4-thread overlock | Side seams and shoulders on knits, stronger than 504 |
| 602 / 605 | 2-needle and 3-needle coverstitch | Hems and necklines on T-shirts and sportswear, stretchy and flat |
| 607 | Flatlock | Flat, strong seams in activewear and some streetwear |
Where each is used on common garments
- T-shirt: 4-thread overlock on shoulders and side seams, coverstitch on neck and hem, sometimes tape in the shoulder seam.
- Hoodie: overlock on most seams, coverstitch or topstitch on hood edge, kangaroo pocket and hem.
- Woven shirt: lockstitch on most seams, with felled or French seams for a clean inside.
- Activewear: flatlock or coverstitch where chafing matters.
How to write construction notes
- List each area: neck, shoulder, side seam, sleeve, hem, pocket.
- State the stitch type or its name for each area.
- Add stitch density, for example 10–12 stitches per inch, and the seam allowance.
- Mention any reinforcement, such as shoulder tape or bar tacks.
- Add a close-up sketch or photo for details the factory may not know.
Stitch density and thread
Stitch density is the number of stitches per inch (SPI) or per 3 cm. More stitches make a firmer seam but take longer and can pucker light fabric. Specify thread type and size too, because spun polyester is common for general sewing and nylon or core-spun for extra strength.
Mistakes to avoid
- Writing only 'double needle' without saying where.
- Using a lockstitch on stretch seams, which can pop when worn.
- Not defining the hem and neck finishes.
- Forgetting seam allowance for the pattern.