A zipper is a small machine sewn into cloth. Buyers who treat it as “a colour and a length” discover that on the line: the slider walks off the chain, the pin misses the box, or the tape shrinks a different amount from the shell. TrimGem University starts here because the same vocabulary sits on every garment BOM — jackets, jeans, bags, kidswear — and the catalogue of closures the Guangzhou desk samples will keep expanding.
Tape, bead and chain
The tape is the woven or knitted band that carries the rest of the zipper. Apparel tapes are usually polyester; cotton and mixed tapes still appear where a mill wants a cotton-like hand or a needle-detectable story. The thickened edge of the tape is the bead. On metal and moulded-plastic zippers the bead is the rail the elements (teeth, scoops) clamp onto. On a coil (nylon) zipper a filler cord sits inside the spiral so the coil has a core to wind around.
Two rows of elements, staggered so they interlock, make a chain. Each row fixed to its tape is a stringer. When the two stringers are meshed you have the zipper chain a factory cuts to length. The tape beyond the elements is the end tape: front (top-stop end) and back (bottom-stop or separable end).
Slider, puller and stops
The slider is the travelling piece whose internal channel forces the two rows of elements to mesh or to split. Its mouth height and mouth width must match the chain gauge. A tenth of a millimetre off and the slider either chews the elements or rides too loose and the chain bursts under side pull.
The puller (tab) is the handle. It may rivet directly to the slider body or hang from a connector. Auto-lock sliders carry a spring pin that drops into the chain when the puller is released; non-lock sliders rely on garment tension.
Top stops keep the slider from running off the top of the chain. A bottom stop on a closed-end zipper keeps the two stringers from separating completely. On a separating (open-end) zipper there is no bottom stop: one stringer carries a pin, the other a box. The wearer inserts the pin fully into the box before the slider will run. Two-way openers add a second slider and, on some constructions, a second pin. Reinforcement film under the pin and box is there because that joint sees the highest peel.
Closed, open and two-way
Closed-end zippers (pockets, fly, dress back) have a fixed bottom stop. Open-end zippers (jacket fronts) separate completely. Two-way closed (X or O, two sliders that cannot leave the chain) and two-way open (two sliders, fully separable) are coat and bag tools. A single-side open-end exists on coil and moulded chains for hoods and removable linings.
Lock function is independent of that geometry: auto-lock, semi-auto-lock, or non-lock. Kidswear programmes often specify moulded plastic top and bottom stops so the ends have no sharp metal corners.
What belongs on the spec
Name the chain type (metal, coil, moulded plastic), the gauge (#3, #5, #8…), closed or open, slider lock type, tape fibre and width, stop material, and whether the pin-and-box set is left-insert or right-insert. Colour is a tape dye lot, not a Pantone on the slider. Fastness of the tape — wash, rub, and transfer onto coated shells — is a zipper test, not a fabric test.
TrimGem samples zippers as assemblies: chain + slider + puller + stops. A pretty puller without a matched mouth is not a closure.