Jakjitech pack makerLast updated October 7, 2026 · about 7 min read
1. What is a tech pack?
A tech pack (called jakeop jisiseo, or jakji for short, in Korean factories) is the document a designer gives a factory saying "please make this garment exactly like this". Different people imagine different garments from the same photo, so the tech pack replaces words with drawings and numbers.
The more complete it is, the fewer sample rounds you need and the more consistent sizes are in bulk production. If items are missing, the factory fills them in from its own experience — and when the result isn't what you wanted, it's hard to say whose fault it was.
2. The 6 parts of a tech pack
| Part | What goes in | Why it matters |
|---|---|---|
| Header | Brand, style number, season, date, item name, sizes, quantity, due date, colors | Keeps documents from getting mixed up in a factory running many styles at once. |
| Flat sketches | Line drawings of the front and back, with measurement codes | Shows seams, topstitching and pocket positions that a photo can't. |
| Size spec | Points of measure, how to measure, measurements per size, grade | The most important part: it fixes how many centimeters the finished garment must be. |
| Fabric & trims | Fabric name, composition, weight/weave, consumption, button/zipper/label specs and quantities | The basis for ordering materials and costing. |
| Sewing spec | Which seam is sewn how, and how wide | The same garment differs in quality and labor cost depending on construction. |
| Notes | Shrinkage, sample approval, thread color, packing | Prevents common mistakes in advance. |
3. Drawing flat sketches
A flat sketch is a line drawing of the garment laid flat and seen from above. It doesn't need to look like fashion illustration — symmetry and proportion matter more.
- Draw front and back side by side. Back-only details like yokes, back pockets and zippers are easy to forget.
- Use bold outlines and thin inner lines so it's easy to read.
- Show topstitching as dashed lines, noting how many rows and how far from the edge.
- Draw rib knit with tight vertical lines and zippers with a bold line and puller.
- Mark measuring points with codes like A, B, C… that match the size spec. Codes keep the drawing clean and avoid confusion about positions.
4. Measuring (flat, half measurements)
Korean tech packs mostly use flat (half) measurements: lay the garment flat and measure straight across from edge to edge — half the circumference. A chest width of 55cm means a 110cm chest circumference. Always state above the table whether you use half or full measurements.
Tops
| Point | Where to measure |
|---|---|
| Body length | From the high point shoulder (where the shoulder seam meets the neck) straight down to the hem. Shirts and jackets are often measured from center back neck. |
| Shoulder width | Straight from one shoulder point to the other |
| Chest width | Side seam to side seam, 1cm below the armhole seam |
| Hem width | Straight across the hem; rib hems unstretched |
| Sleeve length | From shoulder point to sleeve end along the outer sleeve |
| Bicep width | Across the sleeve at the underarm |
| Neck width · front neck drop | Side neck point to side neck point / from the line between side neck points down to center front neck |
Bottoms
| Point | Where to measure |
|---|---|
| Waist width | Straight along the top of the waistband. For elastic waists, give both relaxed and stretched values. |
| Hip width | Across at 2/3 of the rise (skirts: about 18cm below the waist) |
| Thigh width | Across the leg 2cm below the crotch seam |
| Front rise | From center front at the top of the waist to the crotch point |
| Hem width | Straight across the leg opening |
| Total length | From the top of the waist to the hem along the side seam |
Also write a tolerance — usually ±1cm, around ±1.5cm for long measurements like length. When the sample arrives, measure it the same way and correct the table.
5. Korean size labels, letter sizes and waist inches
In Korea, tops are often labeled by chest size (men 90·95·100, women 44·55·66) and bottoms by waist inches (28, 30, 32…). Jakji uses Korean labels and shows letter sizes alongside in the English view. The table below is our reference mapping; brands differ.
| Men (KR) | 80 | 85 | 90 | 95 | 100 | 105 | 110 |
|---|---|---|---|---|---|---|---|
| Letter (ref.) | XXS | XS | S | M | L | XL | XXL |
| Waist inches (ref.) | 28 | 29 | 30 | 31 | 32 | 34 | 36 |
| Women (KR) | 44 | 55 | 66 | 77 | 88 |
|---|---|---|---|---|---|
| Letter (ref.) | XS | S | M | L | XL |
| Waist inches (ref.) | 24 | 26 | 28 | 30 | 32 |
Choose one base (sample) size and write how much each other size grows or shrinks per size (the grade). Samples are usually made in men's 100 (L) and women's 66 (M). Jakji's base values are regular-fit references checked against 16 published measurement charts from two Korean brands (October 2026).
6. Sewing terms you should know
| Term (Korean) | Meaning |
|---|---|
| Overlock (오버록) | Wraps thread around the fabric edge so it won't fray. Knits are often joined directly with an overlock; called 3-thread or 4-thread by the number of threads. |
| Coverstitch (커버스티치, 삼봉) | 2–3 parallel straight rows outside with looped thread covering the inside. Common on T-shirt hems and sleeve hems. |
| 2-needle (2본침, 쌍침) | Two parallel rows sewn at once with two needles, for seams that must be strong, like jeans and shirt side seams. |
| Topstitch (상침) | A visible stitch on the outside, decorative and holding the seam allowance down. Note the distance from the edge, e.g. "topstitch 0.6cm". |
| Rib (시보리) | Stretchy ribbed knit fabric attached at the neckline, cuffs and hem. |
| Pressed open / French seam (가름솔 / 통솔) | Pressed open splits the seam allowance to both sides; a French seam encloses it with two rows of stitching. |
| Interlining (심지) | Reinforcement inside collars, cuffs and waistbands to hold shape. Iron-on fusible interlining is common. |
| Invisible zipper (콘솔 지퍼) | A concealed zipper whose teeth don't show from the outside, often at the center back of skirts and dresses. |
| Blind stitch (공그르기) | Hand or machine stitch that holds a hem with almost no visible stitches outside. |
| Bartack (바택) | Dense repeated stitching that reinforces stress points like pocket corners and belt loop ends. |
| Stitch density (땀수) | Number of stitches in a set length (usually 3cm). More stitches = tighter and stronger. |
| Consumption (요척) | Fabric length needed for one garment; the basis for fabric orders and costing. Confirmed with a marker after the pattern is made. |
7. Checklist before sending to a factory
- Did you write the style number, colors, quantity per size and due date?
- Do the front and back flats show all pockets, seams and topstitching?
- Does the size spec say half or full measurements? Do measuring points match the flat sketch codes?
- Did you write the base size, grade per size and tolerance?
- Did you write fabric composition and weight, and trim specs (button size, zipper length)?
- Did you check fabric shrinkage? Fabrics that shrink a lot must be flagged before cutting.
- Did you decide the care label content? (In Korea: composition, manufacturer, country, date, size, care instructions, labeler address and phone.)
- Is the reference photo your own design or sample? Copying another brand's product shape can be illegal.
The Production tab's ‘Missing items’ check covers most of this list automatically.
More in-depth guides (fabric, costing, sizing, care labels, sample inspection, flats, sewing terms, washing) are currently available in Korean.
Try it with what you just read
Pick an item and the flats, size spec and sewing spec fill in automatically.