Chapter 02
How the Placket and Zip Are Constructed on Each:
This is the chapter most brands skip. Don’t.
The placket is the strip of fabric that carries the zip.
How it is built, and which zip sits inside it, decides your cost, your quality risk, and your factory’s workload.
Two builds, two very different jobs.
The half-zip uses a closed-end zip:
A half-zip carries a closed-end zip. “Closed-end” means the bottom stays fastened.
The slider can never run off the chain, because a stop blocks it.
The zip terminates partway down the chest.
Below that point, the front is one continuous piece of fabric.
The placket is sewn into a slit, and the bottom of the zip is anchored and bartacked inside the garment.
This build is forgiving. Closed-end zips are easy to source.
You can buy them ready-made or make them from continuous zip chains cut to length and closed at the bottom.
That flexibility is a real production advantage.
The full-zip uses a separating zip:
A full zip needs a separating zip. Separating means the two sides come fully apart at the bottom.
That split is made possible by two parts at the base: an insertion pin on one side and a retainer box on the other.
You feed the pin into the box, then zip up.
This pin-and-box is what lets a jacket open all the way.
Here is the catch. That pin-and-box is fixed onto the tape under high heat and high pressure.
It is machine-made only. You cannot attach it by hand, and you cannot make a separating zip from the chain by the yard.
You buy it finished, at the exact length, every time.
So a full-zip locks you into a more specialized, less flexible component from the start.
Slider locking is part of the spec:
A long, vertical front opening has a habit of creeping open on its own.
To stop that, a full-front zip usually wants an auto-lock or semi-auto-lock slider that grips the chain and holds position when you let go.
A half-zip is shorter and sits higher, so the pressure to self-open is lower.
You can still spec a locking slider for feel and quality, but it is less critical.
Either way, put it in your tech pack; it’s an easy line to forget.
Gauge and material, kept simple:
Zips are sized by gauge, written with a hash: #3 #5 #8. The number is the chain width in millimeters.
Bigger number, heavier, and more rugged.
For hoodies, the common picks are a #3 or #5 nylon coil or a #5 to #8 molded plastic (often called Vislon), with chain widths around 5-8 mm depending on how heavy the fleece is.
The coil sits flatter and softer. Molded plastic reads chunkier and sportier.
A half-zip can comfortably run a lighter coil; a full-zip carrying the whole front often steps up because it does more work.
Why alignment is the hidden quality risk:
On a full-zip, both tape edges run the entire body.
They must finish dead level at the hem and match at the collar seam.
Tolerances are tight; even a 2 mm misalignment can make the slider jam or pull the front panel out of true.
Good factories pre-baste with position markers, sew with a twin-needle lockstitch at a 2-3 mm seam allowance, then press and inspect the front edge flat.
A half-zip has far less tape to align, and the lower front is fixed, so its alignment risk is smaller.
That lower risk is one reason half-zips are kinder on a first run.