Garment Assembly Sheets
[ Tech Pack Series ]
Last Update: June 14, 2025
A tech pack links a designer’s creative vision with the actual production of the garment. When done properly, it accelerates timelines, reduces sampling costs, and fosters stronger relationships with suppliers. At the core of that pack is the garment assembly sheet, the detailed construction guide that transforms sketches into stitches. When this page is unclear, garment assembly-sheet mistakes can slip in and multiply into errors on the factory floor. A single oversight can add 2–3 weeks and around €1 per piece in re-work.
After more than 20 years as a product developer, I still notice the same recurring construction mistakes. Errors that disappear when you follow a few simple habits and communicate visually. Below you’ll find the three most common mistakes that impact time, cost, and final quality, along with quick, practical tips to avoid them.
Top 3 Mistakes... and Quick Actionable Fixes
1. Lack of information > Avoid incomplete specs
If it’s not written or illustrated, the manufacturer will decide for themselves… and it often doesn’t match your idea.
That is by far the most common mistake. It shows up in many ways:
No visual references
A written description isn’t enough when the garment has unique design details. Most of these need visual support, like photos or sketches.
Best practices: Adjust and reuse sketches or photos from previous, similar designs.
Incomplete flats or sketches
A front view isn’t enough. You need the back view and any design details that require additional info.
Best practices: Add call-outs for complex constructions. They help eliminate guesswork.
Poor construction details
This mistake happens in different ways, but the 2 most common are:
- Ignoring seam structure: we don’t clearly explain how a part of the garment should be assembled. For example, writing “1/4″ Flatlock Stitch centred over seam” missing the seam’s structure leads to multiple interpretations.
- Undefined internal finishes: are the seams polished with overlock, bound, or left with raw edge? Finishing affects cost, production time, machinery, and the final look of the garment.
Some measurement details must also be clear and precise. For example, button sizes must be specified to make the correct buttonhole size, or hems that are wider than usual but don’t include the exact width.
Best practices: support each detail with clear call-outs or sketches that visually show the exact construction. Also, use our ASCS seam diagrams to show the seam structure and finish clearly. That is especially important for high-end garments.
2. Lack of clarity > Stop ambiguous call-outs
Ambiguity leads to more clarification emails than missing information. It usually shows up like this:
Inconsistency between text and drawing.
This problem arises when the written notes don’t match what the sketch shows, forcing the factory to guess which reference is correct. For example, if your pants sketch illustrates a standard hem of 12–15 mm but the note calls for 35 mm, the manufacturer has to stop and ask for clarification or choose one of the options by themselves.
Best practice: Treat the flat as the single source of truth. Make sure every measurement, seam, and detail in the notes aligns with what’s on the page, and add text only when it clarifies something the drawing can’t show on its own.
Regional or ambiguous terminology.
A single seam can have several names and abbreviation styles, even within the same country. When I worked in Switzerland, one of my designers called a rolled hem a “baby hem,” while her colleague within the same team used the term “ruloté” for the exact same construction.
Best practice: Illustrate seams with clear sketches so the structure speaks for itself. That way, you don’t have to rely on names and ensure your manufacturer understands.
Unnecessary or repeated information
Naming every part of the garment usually adds little value and buries the details that really matter. For example, if your flat already shows a back yoke on the shirt, there’s no need to mention it again in the notes.
Repeating information by writing can be a good technique to reinforce important information. However, abusing this technique by describing any information turns the tech pack into a scavenger hunt. For example, if the stitch placement is clearly drawn, there’s no need to explain it in words.
Best practices: Let the visuals do the heavy lifting—use flats, sketches, and call-outs to show the construction, and add written notes only when they provide essential clarification.
Low-quality or poorly scaled images
A disproportionated sketch or a pixelated image can make the reader second-guess your intent.
Best practices: Make sure the sketches you use proportionally represent your flats. Also, avoid using images under 300 dpi.
3. Poor organisation> Organise your layout
A tech pack can be technically complete, but if the structure doesn’t guide the reader, time is lost trying to find the right information. That leads to mistakes.
Too much on one page
Mixing the assembly sheet with embroidery details and a colour palette overloads the reader with no relevant information.
Best practices: Keep sections separate and organized in a way that works for the reader. In this case, the pattern maker and manufacturer.
Confusing reading flow
Highlighting key info helps the manufacturer understand what’s most important.
Best practices: Use different font sizes or colour highlights to make the critical information stand out.
Missing pagination
In tech packs with three or more pages, having clear page numbers prevents information from getting lost.
Best practices: Make sure your tech pack has page numbers set up by default.
Bonus – Mistake 4: Not updating the tech pack after a design change
Design changes need to be reflected in the current version of the tech pack and in the revision history. Working with outdated files can lead to errors that affect the entire production run.
Summary
- Lack of information and lack of clarity silently waste time and money. Poor organization makes it harder to use even the best data effectively.
- Regularly reviewing your communication process will turn your tech pack into a powerful tool… not just a file on your computer.
- Every minute spent making your communication more precise will save you hours of changes and fixes later on. Start by reviewing your latest tech pack using these three points and see how much smoother your next round of protos goes.
FAQs
5 Frequently-Asked Questions about Garment Assembly Sheets
A garment assembly sheet is the set of illustrated pages inside a tech-pack that show how every seam, stitch, trim and panel come together—essentially the road map that turns 2-D pattern pieces into a 3-D garment. (techpacker.com)
The tech pack is the complete production blueprint (measurements, BOM, colorways, QC, etc.); the assembly sheet is just one component that zooms in on construction order, seam types and stitch specs so the factory knows how to build the style. (techpacker.com)
A garment assembly sheet contains construction data. For example, it specifies the seam type, stitch and topstitch details for each part, the stitch density (SPCM or SPI), any necessary reinforcements or edge finishes (such as bartacks, stay-tape, clean-bind, cover-hem), and critical construction measurements with call-outs for complex areas like gussets or plackets. It provides everything the operator needs to assemble the garment.
Precise construction notes cut sampling rounds, reduce fit comments and keep fast-track calendars on time—ultimately saving cost and speeding time-to-market. (techpacker.com, TECHPACKS.CO)
Typically the technical designer or product developer creates it in collaboration with the designer, then updates it whenever the style changes; the manufacturer reviews and flags anything unclear. (TECHPACKS.CO)
If you haven’t yet, try our seam diagrams. They’ll save you time and help ensure accurate construction and finishing details. More info here: ABC Seams Code System (ASCS)
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Belu Chi
Technical Designer at ABC Seams®
Belu Chi is a fashion product developer and the founder of ABC Seams® Pty. Ltd. With over 20 years of experience working with brands ranging from Burberry and Karl Lagerfeld to fast fashion and emerging labels. She currently writes reference books that standardise seam communication for designers and manufacturers worldwide.
Consulted and Related Sources
- Kochar, S. (2023, January 12). The ultimate guide to tech packs in fashion. Techpacker. https://techpacker.com/blog/design/what-is-a-tech-pack/
- Lentz, M. (2025, March 25). Tech packs 101: Avoid these common mistakes to perfect your fashion design process. Pham Fashion House. https://www.phamfashion.com/blog/tech-packs-101-common-mistakes-designers-fix
- Munger, L. (n.d.). Down coat extreme jacket: Tech-pack example. Liuba Munger. Retrieved June 25, 2025, from https://liubamunger.com/down-coat-extreme-jkt
- Sew Heidi. (2025, February 27). What is a tech pack & why do you need one? Real-life examples + step-by-step guide. Successful Fashion Designer. https://successfulfashiondesigner.com/tech-pack-step-by-step/
- Techpacker. (n.d.). Garment assembly: How to explain constructions effectively to your manufacturer. Retrieved June 25, 2025, from https://techpacker.com/blog/manufacturing/garment-assembly-how-to-explain-constructions-effectively-to-your-manufacturer/
- Techpacks.co. (2020). Garment assembly: Why & how to specify it. https://www.techpacks.co/blog/garment-assembly-why-and-how-to-specify-it
- Uphance. (2024, May 23). 7 tech pack mistakes every designer should avoid. Uphance. https://www.uphance.com/blog/tech-pack-mistakes-to-avoid/
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