# Craft Fasteners, Closures & Hardware

This leaf bundles seven unrelated closure mechanisms, so the type decides the spec sheet before anything else does: a button's ligne size, a zipper's gauge, a snap's rivet parts, and a buckle's webbing width share no columns. End use then decides which property of that type's hardware actually matters.

## How it works

Most items in this leaf fasten one of three ways. A button, snap or hook-and-eye interlocks two small preformed parts by hand, and is reusable indefinitely without wearing out. A zipper uses a slider to mesh a long row of teeth or a wound coil, so one motion closes the whole length at once. Hook-and-loop bonds by mechanical friction between thousands of nylon hooks and loops (or, in heavy-duty versions, mushroom-shaped stems), so it grips instantly but the hooks wear smooth over repeated cycles. The rest — grommets, rivets, buckles, D-rings, cord locks — are hardware rather than closures: a grommet or rivet is permanently set through punched material with a tool and never comes apart again, while a buckle, D-ring or cord lock is sized to a webbing width and routes or locks a strap without piercing it.

## How an expert narrows the choice

```mermaid
timeline
  section 1 · Closure type
    button : ask Button attachment, Button material, Button size : skip Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material
    snap_fastener : ask Snap mechanism : skip Button attachment, Button material, Button size, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material
    zipper : ask Zipper tooth material, Zipper gauge, Zipper mechanism : skip Button attachment, Button material, Button size, Snap mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material
    hook_and_loop : ask Hook-and-loop backing, Hook-and-loop style : skip Button attachment, Button material, Button size, Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material
    hook_and_eye : ask Hook-and-eye form : skip Button attachment, Button material, Button size, Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material
    structural_hardware : ask Hardware subtype : skip Button attachment, Button material, Button size, Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form
  section 2 · Hardware subtype
    grommet_eyelet : ask Grommet/eyelet size class, Grommet/eyelet material : skip Rivet style, Strap hardware width, Strap hardware type, Strap hardware material
    rivet : ask Rivet style : skip Grommet/eyelet size class, Grommet/eyelet material, Strap hardware width, Strap hardware type, Strap hardware material
    strap_hardware : ask Strap hardware width, Strap hardware type, Strap hardware material : skip Grommet/eyelet size class, Grommet/eyelet material, Rivet style
  section 3 · Project end use
    Apparel touching skin, bags and leather goods, or outdoor and marine gear?
```

1. **Closure type.** Buttons, snaps, zippers, hook-and-loop, hooks-and-eyes, or hardware like grommets and buckles?
   Each type's spec sheet is disjoint: a button's ligne size, a zipper's gauge and a snap's rivet parts never share a column, so this fork decides which facet set to ask next.
   If button: ask Button attachment, Button material, Button size; skip Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material.
   If snap_fastener: ask Snap mechanism; skip Button attachment, Button material, Button size, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material.
   If zipper: ask Zipper tooth material, Zipper gauge, Zipper mechanism; skip Button attachment, Button material, Button size, Snap mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material.
   If hook_and_loop: ask Hook-and-loop backing, Hook-and-loop style; skip Button attachment, Button material, Button size, Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-eye form, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material.
   If hook_and_eye: ask Hook-and-eye form; skip Button attachment, Button material, Button size, Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hardware subtype, Grommet/eyelet size class, Grommet/eyelet material, Rivet style, Strap hardware width, Strap hardware type, Strap hardware material.
   If structural_hardware: ask Hardware subtype; skip Button attachment, Button material, Button size, Snap mechanism, Zipper tooth material, Zipper gauge, Zipper mechanism, Hook-and-loop backing, Hook-and-loop style, Hook-and-eye form.
   Skip if already known: a query that already names the closure type, a title containing 'button', 'snap', 'zipper', 'velcro', 'hook and eye', 'grommet', 'rivet' or 'buckle'.

2. **Hardware subtype.** Grommets and eyelets, rivets, or strap hardware like buckles and D-rings?
   Grommets, rivets and strap hardware are all 'structural_hardware' but compare on different attributes, so this second fork only fires once closure_type has already said 'hardware'.
   If grommet_eyelet: ask Grommet/eyelet size class, Grommet/eyelet material; skip Rivet style, Strap hardware width, Strap hardware type, Strap hardware material.
   If rivet: ask Rivet style; skip Grommet/eyelet size class, Grommet/eyelet material, Strap hardware width, Strap hardware type, Strap hardware material.
   If strap_hardware: ask Strap hardware width, Strap hardware type, Strap hardware material; skip Grommet/eyelet size class, Grommet/eyelet material, Rivet style.
   Skip if already known: a title naming grommet, eyelet, rivet, buckle, D-ring, cord lock or triglide.

3. **Project end use.** Apparel touching skin, bags and leather goods, or outdoor and marine gear?
   End use decides which judgement attaches to the same hardware: skin contact raises nickel-release rules, straps raise load-bearing concerns, and outdoor gear raises corrosion.
   Skip if already known: a query naming the finished project (shirt, bag, tent, jacket).

## What to surface

### Closure type

Which family of fastener this is: button, snap, zipper, hook-and-loop, hook-and-eye, or structural hardware (grommets, rivets, strap hardware). It decides which spec sheet applies at all; a button's ligne size and a zipper's gauge number are not comparable quantities, so asking this first avoids asking about tooth material on a button. [1] [2] [4]

Values: button, snap_fastener, zipper, hook_and_loop, hook_and_eye, structural_hardware.
Question to ask: Buttons, snaps, zippers, hook-and-loop, hooks-and-eyes, or hardware like grommets and buckles?

Used as: top-level split, filter. Data: derived from listing fields, backfill cost low. Look for it as: Derive from the product title; these terms are almost always present verbatim.
Title keyword match covers nearly every listing in this leaf.

### Hardware subtype

Within structural hardware: a grommet/eyelet, a rivet, or strap hardware (buckle, D-ring, cord lock, clasp). A grommet reinforces a punched hole, a rivet permanently joins two layers, and strap hardware routes or locks webbing; none of their spec sheets overlap. [7] [8] [12]

Values: grommet_eyelet, rivet, strap_hardware.
Question to ask: Grommets and eyelets, rivets, or strap hardware like buckles and D-rings?

Used as: top-level split, filter. Data: derived from listing fields, backfill cost low. Look for it as: Derive from the title once closure_type is 'structural_hardware'.
Title keyword match ('grommet', 'eyelet', 'rivet', 'buckle', 'D-ring', 'cord lock').

### Project end use

Whether the finished item touches skin (apparel), is a bag/leather good, or is outdoor/marine gear. Skin-contact apparel raises nickel-release and CPSIA small-parts concerns on metal hardware; bags and outdoor gear raise load-bearing and corrosion concerns instead. [13] [14] [11]

Values: apparel_skin_contact, bags_leather_goods, outdoor_marine.
Question to ask: Apparel touching skin, bags and leather goods, or outdoor and marine gear?

Used as: top-level split, filter, shown on the card. Data: needs research, backfill cost medium. Look for it as: Rarely a listing field; infer from the product's marketed use (kidswear snaps, bag hardware, marine zippers).
Keyword-match the title/category against apparel, bag/leather, or outdoor/marine terms; default to apparel_skin_contact when unclear since it is the most common craft use.

### Strap hardware width

The webbing width the hardware is sized to fit, as a trade size: under 1 inch, 1 inch, 1.5 inch, or 2 inch and wider. A buckle, D-ring or cord lock only works with webbing within a narrow width tolerance; the wrong width either falls through or won't thread at all, so this is the single must-match spec before anything else about the hardware. [12] [11]

Values: under_1_inch, one_inch, one_point_5_inch, two_inch_or_wider, unspecified.
Question to ask: What width is the strap or webbing it needs to fit?

Used as: filter, sortable. Data: on the listing, backfill cost low. Look for it as: Usually stated directly in the title or spec line ('1in Side Release Buckle').
Title keyword match for the stated inch size.
Chart: position on a width axis.

### Strap hardware type

The hardware's own job: side-release buckle, D-ring, ladder lock/slider, cord lock, swivel clasp, cam buckle, swivel snap hook, or locking buckle. Each does a different strap job: a side-release buckle gives a quick-disconnect joint, a ladder lock/triglide or cam buckle adjusts length, a D-ring anchors a strap, a cord lock grips only a drawstring, a swivel clasp or snap hook clips a leash on and spins free, and a locking buckle resists being opened by hand. [12] [17]

Values: side_release_buckle, d_ring, ladder_lock_slider, cord_lock, swivel_clasp, cam_buckle, swivel_snap_hook, locking_buckle, unspecified.
Question to ask: Which job: buckle, D-ring, adjuster, cord lock, snap hook, or locking buckle?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title or product family name ('Side Release Buckle', 'Triglide Slider', 'Swivel Snap Hook', 'Key Locking Buckle').
Title keyword match against the eight named types.

### Zipper gauge

The chain-width number stamped on the slider, with common sizes #3, #5, #7, #8 and #10; the bigger the number, the wider and stronger the zipper. A replacement slider or zipper must match the original gauge or it won't engage the teeth; garment zippers are usually #3–#5 while bags and tents use #8–#10 for strength. [1]


Used as: filter, sortable. Data: on the listing, backfill cost low. Look for it as: Stamped on the slider pull itself, and usually repeated in the listing title ('#5 Zipper').
If missing, this register's own inference (not a cited spec) is #3 light garments, #5 jackets/bags, #8–#10 heavy/outdoor; treat as a guess, not a manufacturer rule.
Chart: position on a size axis from light garment to heavy-duty.

### Zipper mechanism

How the zipper opens: closed at both ends, open-ended/separating with a box-and-pin, two-way with a puller on each end, or invisible (teeth hidden behind the tape). A separating zipper is required for a jacket that opens into two pieces; an invisible zipper is chosen specifically so no teeth show on a dress or skirt; a closed-end zipper is the default for pouches and plain garments. [1]

Values: closed_end, open_end_separating, two_way_separating, invisible, unspecified.
Question to ask: Fully separate into two pieces, or stay joined at the bottom?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Separating Zipper', 'Invisible Zipper').
Title keyword match; default to closed_end when unspecified.

### Button attachment

How the button is sewn on: through flat holes (2 or 4), or through a raised shank on the back. A shank button sits proud of the fabric and suits thick coats; a flat sew-through button lies closer to the fabric and suits shirts, so the wrong style changes how the garment drapes at the closure. [2]

Values: sew_through_2_hole, sew_through_4_hole, shank, unspecified.
Question to ask: Flat holes you sew through, or a raised shank on the back?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('4-Hole Button', 'Shank Button') or visible in the product photo.
Title keyword match; default to sew_through_4_hole when unspecified, the most common style.

### Button material

What the button is made of: plastic/resin, wood, shell (mother-of-pearl), metal, or horn. Material sets both look and wash durability: shell and metal survive machine washing and dry cleaning better than wood or cheap resin, which can crack or discolor. [2]

Values: plastic_resin, wood, shell_mother_of_pearl, metal, horn, fabric_covered, unspecified.
Question to ask: Plastic, wood, shell, or metal?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Almost always in the title ('Mother of Pearl Button', 'Wood Button').
Title keyword match; default to plastic_resin when the title says nothing, the most common and cheapest material.

### Button size

The button's size, measured in the trade's own unit, the ligne (40 lignes to an inch). Buttonholes are cut to the ligne size, not a guess, so the wrong number means the button won't sit in the hole; shirt buttons run around 16L (about 10mm) and suit/coat buttons around 32L (about 20mm). [2] [3]


Used as: filter, sortable. Data: on the listing, backfill cost low. Look for it as: Listed as 'L' or 'ligne' size, or a mm diameter the buyer must convert.
Most listings give a mm diameter; divide by 0.635 to get the ligne size if needed.
Chart: position on a size axis from shirt (small) to coat (large).

### Snap mechanism

How the snap is attached and closes: sewn on through holes, set with a tool as a 4-part rivet snap (eyelet, socket, cap, stud), or a turn-clasp. A sew-on snap needs no tool and can be removed by unpicking thread; a rivet-set press snap needs pliers or a press and, once set, is effectively permanent; a turn-clasp is a rotating metal tab snap rather than a spring stud, used on leather goods and coats. [4] [5] [6]

Values: sew_on_snap, press_snap_tool_set, turn_clasp, unspecified.
Question to ask: A snap you sew on, or one you set with a tool?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Sew-On Snaps', 'Metal Snap Fasteners Kit with Pliers').
Title keyword match; a listing bundling a setting tool or die is almost always press_snap_tool_set.

### Zipper tooth material

What the zipper's teeth are made of: a continuous polyester/nylon coil, molded plastic teeth, or individual metal teeth. Coil zippers are flexible and cheap and dominate most garments; metal teeth are stronger and used in jeans and workwear; molded plastic teeth are easiest to color-match and common in bags and pouches. [1]

Values: coil_polyester_nylon, molded_plastic_tooth, metal_tooth, unspecified.
Question to ask: Coil, molded plastic teeth, or metal teeth?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('#5 Nylon Coil Zipper', 'Metal Zipper').
Title keyword match; default to coil_polyester_nylon when unspecified, the most common type.

### Hook-and-loop backing

How the hook-and-loop tape attaches to the material: sewn on, or a pressure-sensitive adhesive (PSA) backing that sticks on its own. Sew-on tape survives washing and heavy use; adhesive-backed tape goes on in seconds with no needle but can peel off a fabric that flexes or gets washed often. [10]

Values: sew_on, adhesive_psa, both_sides_different, unspecified.
Question to ask: Sew it on, or stick it on?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Sew-On Hook and Loop', 'Self-Adhesive Velcro Tape').
Title keyword match; default to sew_on for fabric tape and adhesive_psa for craft/mounting tape.

### Grommet/eyelet size class

Which job's size it is: a small lacing eyelet (shoes, corsets), a medium curtain/craft grommet, or a large tarp/sail grommet. The setting tool, the cord or lace that must pass through, and the load it will see are all set by which of these three jobs the grommet is for; a shoe eyelet die will not set a tarp grommet. [7]

Values: lacing_eyelet_small, curtain_craft_medium, tarp_sail_large, unspecified.
Question to ask: A small lacing eyelet, a curtain-size grommet, or a large tarp/sail grommet?

Used as: filter, shown on the card. Data: derived from listing fields, backfill cost medium. Look for it as: Implied by the marketed use ('Shoe Eyelets', 'Curtain Grommets', 'Tarp Grommet Kit') rather than a stated size number — inferred the same way closure_type is, not read off a spec line.
Keyword-match the title's stated use; default to curtain_craft_medium when unclear.

### Rivet style

Double-cap (a decorative cap on both faces), single-cap (a cap on one face, a visible hole on the other), a cutlery rivet for attaching a handle, or a semi-tubular rivet (hollow shaft, sets with less force than a solid rivet). Double-cap rivets are the decorative choice on bags and leather goods since both sides look finished; single-cap is cheaper and used where only one face shows; cutlery rivets join a knife handle to its blade; semi-tubular rivets need less force to set, so they work with hand tools instead of a press. [8]

Values: double_cap, single_cap, cutlery_rivet, semi_tubular, unspecified.
Question to ask: Caps on both sides, one side, or a knife handle?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Double Cap Rivets', 'Knife Handle Rivets').
Title keyword match; default to double_cap for leathercraft listings.

### Strap hardware material

What the hardware itself is made of: acetal or nylon plastic, zinc-alloy or steel metal, or stainless steel. Plastic hardware is light and won't rust, which is why backpacks and life jackets use it; metal hardware is stronger for the same size and is chosen for load-bearing straps like pet leashes and tool belts, with stainless specifically for marine and outdoor use where plated metal corrodes. [12] [11]

Values: acetal_nylon_plastic, zinc_alloy_or_steel, stainless_steel, unspecified.
Question to ask: Plastic, regular metal, or stainless steel?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Stainless Steel D-Ring', 'Plastic Side Release Buckle').
Title keyword match; default to acetal_nylon_plastic, the most common bag-hardware material.

### Hook-and-loop style

Standard woven hook-and-loop (interlocking nylon hooks and loops) versus a heavy-duty mushroom-stem style that snaps audibly shut. Standard hook-and-loop is quieter and peels apart easily by hand; mushroom-stem versions hold several times tighter and are used where a strap or panel must not pop open on its own. [10]

Values: standard_hook_and_loop, mushroom_stem_heavy_duty, unspecified.

Used as: filter, shown on the card. Data: on the listing, backfill cost medium. Look for it as: Heavy-duty mushroom-stem tape is usually branded ('Dual Lock'-style) and priced noticeably higher per foot.
Default to standard_hook_and_loop unless the listing names a mushroom/dual-lock style.

### Hook-and-eye form

Sold as individual hook-and-eye pairs, or as a continuous ready-to-cut tape with hooks and eyes spaced along it. Individual pairs are placed exactly where a garment needs them (a cloak clasp, a trouser waistband); tape is cut to length and is the standard way bra and corset makers add many closures fast. [9]

Values: individual_pairs, continuous_tape, unspecified.
Question to ask: Separate hooks and eyes, or a continuous strip you cut to length?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Hook and Eye Tape', 'Sew-On Hooks and Eyes').
Title keyword match.

### Grommet/eyelet material

What the grommet or eyelet is made of: metal (often brass or nickel-plated), plastic, or rubber. Metal grommets resist abrasion and hold their shape under repeated lacing or flapping (tarps, sails); plastic and rubber are cheaper and used where the hole just needs a clean edge, not load-bearing strength. [7]

Values: metal_brass_or_plated, plastic, rubber, unspecified.
Question to ask: Metal, plastic, or rubber?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Usually in the title ('Brass Grommets', 'Plastic Eyelets').
Title keyword match; default to metal_brass_or_plated, the most common craft grommet.

## What you give up

- A snap, rivet or shank button doesn't weaken with use the way hook-and-loop does; buy hook-and-loop for quick, low-cycle closures and a snap or rivet for anything opened and closed thousands of times. [10] [8] Board branch: "Reusable now vs. holds its grip over years".
- Rivets and grommets are set once and don't come apart; a sewn snap or button can be moved, replaced or removed by unpicking thread, which rivets and grommets can't. [8] [4] Board branch: "Permanent and strong vs. removable and adjustable".

## Words you will meet

- **Ligne**. The button and snap trade's own size unit; 40 lignes equal 1 inch.
- **Shank**. A raised loop on the back of a button that thread sews through instead of holes in the face.
- **Coil zipper**. A zipper whose teeth are formed from one continuously wound strand of polyester or nylon rather than separate pieces.
- **Zipper gauge**. The chain-width number stamped on a zipper's slider; bigger numbers mean wider, stronger teeth.
- **Separating zipper**. A zipper that opens fully into two unjoined pieces, using a box-and-pin mechanism at the bottom.
- **Invisible zipper**. A zipper whose teeth hide behind the tape so only a thin seam line shows from the front.
- **Press snap / rivet snap**. A snap set with a tool, built from four parts — eyelet, socket, cap and stud — that lock together permanently.
- **Hook-and-loop**. The generic name for Velcro-style fastening: one strip of tiny hooks grips another strip of loops.
- **Mushroom-stem fastener**. A heavy-duty hook-and-loop variant with molded mushroom-shaped stems on both sides instead of hooks and loops.
- **Eyelet**. The common name for a small grommet, used especially on shoes, corsets, tarps and sails.
- **Double-cap rivet**. A rivet with a finished metal cap on both faces, so neither side shows a bare hole.
- **Hook-and-eye tape**. A continuous strip with hooks and eyes spaced along it, cut to length instead of attaching each pair by hand.
- **Webbing**. The flat or tubular woven strap that buckles, D-rings and cord locks are sized to fit around.
- **Nickel release**. How much nickel a metal part sheds onto skin on contact; the EU limits this on items like buttons and zippers worn close to skin.
- **CPSIA small parts**. A US children's-product rule that tests hardware like buttons, snaps and rivets for choking-hazard size on items for kids under 3.

## Where we made a call

- Metal buttons, snaps and zippers in skin contact should carry low nickel release, tested to EN 1811, under the EU limit since 2004. (confidence medium). EN 1811 named as the EU's own prescribed nickel-release test method, now enforced via REACH Annex XVII; still a secondary (Wikipedia) account of the standard, not the standard text itself. [13] [16]
- Button, snap and rivet hardware on children's products is subject to US small-parts test 16 CFR 1501, under the CPSIA 2008–2009 schedule. (confidence medium). 16 CFR 1501 itself (via Cornell LII) confirms the choking/small-parts rule for children under 3; CPSIA's own 'zippers or buttons' sentence is a different, lead-testing passage, not this rule. [14] [15]

## References

1. [Zipper](https://en.wikipedia.org/wiki/Zipper) (primer). Supports: Common zipper gauge sizes are #3, #5, #7, #8 and #10; Coil, molded plastic, and metal tooth constructions and their typical uses; Closed-end, open-end separating, two-way, and invisible zipper mechanisms.
2. [Button](https://en.wikipedia.org/wiki/Button) (primer). Supports: Buttons sized in lignes, 40 lignes to an inch; 16L (10.16mm) shirt buttons and 32L (20.32mm) suit buttons as reference sizes; Sew-through vs shank attachment; plastic, shell, metal, wood materials.
3. [Line (unit)](https://en.wikipedia.org/wiki/Line_(unit)) (primer). Supports: The US button-trade ligne equals 0.635mm (1/40 inch), corroborating the button ligne-to-mm math.
4. [Snap fastener](https://en.wikipedia.org/wiki/Snap_fastener) (primer). Supports: Rivet-set press snaps are built from eyelet, socket, cap and stud parts.
5. [Prym press fasteners category](https://www.prym.com/en/buttons-fasteners/press-fasteners) (spec sheet). Supports: Brand taxonomy separates sew-on snap fasteners from non-sew press fasteners, turn-clasps and magnetic snaps.
6. [Prym metal snap button product pages](https://www.prym.com/en/metal-snap-button-88bf208ecf783a1095d85282f6861ded) (spec sheet). Supports: Example sew-on snap diameters of 23mm and 28mm.
7. [Grommet](https://en.wikipedia.org/wiki/Grommet) (primer). Supports: A small grommet is also called an eyelet, used on shoes, tarps and sails; Grommets are made of metal, plastic or rubber.
8. [Rivet](https://en.wikipedia.org/wiki/Rivet) (primer). Supports: Double-cap rivets have caps on both sides; single-cap rivets have a cap on one side only; Cutlery rivets attach knife handles; semi-tubular rivets need less force to set than solid rivets.
9. [Hook and eye](https://en.wikipedia.org/wiki/Hook_and_eye) (primer). Supports: Hook-and-eye closures are sold individually or as ready-to-cut tape, in steel, nylon-coated wire, or brass.
10. [Hook-and-loop fastener](https://en.wikipedia.org/wiki/Hook-and-loop_fastener) (primer). Supports: Heavy-duty mushroom-stem variants (Dual Lock-type) snap shut audibly and use pressure-sensitive adhesive.
11. [Webbing](https://en.wikipedia.org/wiki/Webbing) (primer). Supports: Webbing breaking strengths are readily available in excess of 10,000 pounds-force; Webbing hardware is sized to the strap's width.
12. [ITW Nexus North America product catalog](https://na.itwnexus.com) (spec sheet). Supports: Strap-hardware product families: side-release buckle, D-ring, ladder lock, cord lock, swivel/triglide, cam buckle; Hardware product names encode webbing width (e.g. a 2 inch side-release buckle body).
13. [Nickel allergy](https://en.wikipedia.org/wiki/Nickel_allergy) (primer). Supports: An EU nickel-release safety directive has been in place since 2004; Metallic buttons and zippers are named sources of nickel skin exposure.
14. [Consumer Product Safety Improvement Act](https://en.wikipedia.org/wiki/Consumer_Product_Safety_Improvement_Act) (primer). Supports: The small-parts rule took effect November 2008 / February 2009.
15. [16 CFR Part 1501, purpose (Cornell LII e-CFR)](https://www.law.cornell.edu/cfr/text/16/1501.1) (regulator). Supports: 16 CFR 1501 is the small-parts test for choking, aspiration or ingestion hazards in children's articles.
16. [Nickel Directive](https://en.wikipedia.org/wiki/Nickel_Directive) (primer). Supports: EN 1811 is the EU's prescribed test method for quantifying nickel release from products; Now enforced as item 27 of REACH Annex XVII rather than a standalone directive.
17. [Carabiner](https://en.wikipedia.org/wiki/Carabiner) (primer). Supports: A swivel-jointed snap hook with a load-bearing latch is the historical strap/luggage-strap form of this hardware.