How to Use a Credit Card Multitool: The Complete Field Guide
Most people meet a card multitool as an object before they meet it as a tool: a flat piece of metal with forty holes in it, no instructions in the envelope, and no obvious place to start. This page is the missing first page of the manual — what each group of cutouts is, who it is for, how it is actually used, and what it does not do.
It is deliberately a hub, not an encyclopedia. Each of the twelve sections below gives you the short working answer in two or three paragraphs, then points to the article, the trainer or the card that goes deeper. If you already know what you are looking for, use the index — the sections are numbered and anchored.
One note before the tools. Everything here is written about milled cards — ours and the handful of others made the same way. If your card came free with a magazine and bends between two fingers, most of the technique below still applies, but the limits are much closer than the ones I quote.
01 · WHAT IT ISWhat a credit-card multitool actually is
A card multitool is one flat plate with tool shapes cut through it. Nothing folds, nothing pivots, nothing is riveted on. The footprint is a bank card — 85 × 55 mm on the Universal series, the Adventur, the Bushcrafter and the OfficeWorker, 87 × 55 mm on the Extreme, and 87 × 54 mm on the two drafting cards. The thickness is where the models separate: 1.5 mm on the Professional and the Designer, 2 mm on the Universal 3.0, the Universal 4.0 in titanium and the OfficeWorker, 2.4 mm on the Universal 5.0, the Bushcrafter and the 440C Universal 4.0, and 3 mm on the Extreme and the Adventur.
Those fractions of a millimetre decide everything else. Bending stiffness rises with the cube of thickness, so a 3 mm Adventur is not 50 per cent stiffer than a 2 mm card — it is roughly three times stiffer, which is exactly why the chopping cards are the thick ones and the drafting cards are the thin ones. Function counts follow the same logic: a Bushcrafter carries twelve survival tools and nothing else, a Universal 4.0 carries more than eighty jobs and between 22 and 57 numbered cutouts across the family.
Those fractions of a millimetre decide everything else.
Why milled and not stamped: a stamping die shears the metal, leaves a rolled edge on one face and a burr on the other, and work-hardens everything near the cut. That is acceptable for a bottle opener and useless for a wrench, because the wrench flat has to be flat and the 13 mm slot has to be 13 mm after heat treatment, not before. Milling holds the tolerance, which is what lets a card grip a nut instead of rounding it. The metal is either hardened 440C at 52–54 HRC or Grade 5 titanium at 35–37 HRC.
02 · ANATOMYAnatomy of the card: front, back, and the numbers
The face with the MRF logo is the front. Hold the card that way up and the layout makes sense: the long edges carry the rulers and the open wrenches, the corners carry the heavy jobs — pry tip, shovel corner, hatchet edge — and the middle of the plate carries the closed shapes that need metal all around them: bit drivers, drill gauges, the sundial hole, the circle template. The back carries the second scale set and whatever did not fit on the front.
INTERACTIVE · 10 CARDSSpin the card and tap a numberEvery card in the series as its real 3D model, with each numbered cutout explained. Open the Tool Explorer →
Reading the engraving takes a minute. Numbers next to a cutout are an index, not a size. Figures with units — 13, 5/16, Ø4.2 — are the size. A Ø means the hole is a gauge: if the drill or the wire goes through, it is that size or smaller. Scales always start at the edge of the plate, so you measure by laying the edge on the work, not by lining up the middle of the card.
Every functional cutout is numbered because no one memorises fifty-seven shapes, and because the number is the link between the metal in your hand and the explanation. Open the Tool Explorer, pick your card, spin the real manufacturing model, tap the number — that is the fastest way to learn a card you already own, and the honest way to inspect one you do not.
03 · WRENCHESWrenches and bolts: how a flat card turns a nut
The open wrenches are notches in the edge of the plate. Slide the notch over two flats of the nut until the metal seats, keep the card in the plane of the nut — not tilted, that is what rounds corners — and pull rather than push, so a slip costs you a knuckle instead of a hand. Grip the card at the far corner: the whole point is to use the diagonal as the arm.
The ranges differ by card. The Universal 3.0 covers 4–15 mm plus the imperial sizes; the Universal 4.0 and 5.0 start at 2.5 mm and run to 15 mm plus imperial; the Extreme is the bolt specialist at 6–17 mm plus 5/16″ to 9/16″, with hex keys and a locking bit driver; the Adventur covers 8–17 mm; the Lumberjack is nothing but wrenches — fourteen hex sizes from 4.5 mm to 9/16″ — plus a comb. The OfficeWorker keeps the small nuts, 6 to 8 mm, for furniture and equipment racks. Spoke keys for 13, 14 and 15 gauge sit on the Universal 3.0 and 4.0 and on the Extreme, and the butterfly and O₂ shapes handle gas and valve fittings.
Now the honest part about torque. A card hands you roughly 50 mm of lever. That is plenty for a bicycle bolt, a saddle clamp, a furniture nut or a loose gas fitting, and it is not plenty for a wheel nut or anything that has been rusting since the last presidency. The Extreme answers exactly that: its torque handle, which comes with the Full Kit, roughly triples the arm and turns a hand-tight card into a proper spanner. A rounded head or a seized fastener is still a job for a socket at home, and a card will not pretend otherwise.
04 · DRIVERS & BITSScrewdrivers and bits: the plate and the bit driver
Flat drivers are milled straight into the plate, usually in two or three widths, including an ultrawide tongue on the Universal 4.0 for battery covers and access panels. Use them the way you would use a screwdriver you are not allowed to lean on: push the card into the slot along the screw axis first, then twist with the plate flat against your palm. The card does not tolerate rocking — the tip is as wide as the slot and as thin as the plate.
A cross-head screwdriver cut into the plate itself exists on three cards: the Universal 5.0, the Extreme and the OfficeWorker. On the Universal 3.0, the Universal 4.0 and the Adventur there is no Phillips shape in the metal — those cards drive cross-head screws through the bit driver, with a bit. That distinction matters more than it sounds, because a bit in a card is stronger than any shape you can mill at 2 mm.
Bit drivers are the quiet workhorse. The 1/4″ hex socket is on almost every card; the Universal 3.0 adds a 1/8″ socket for eyeglass-scale work, the Universal 4.0 and 5.0 add a 4 mm precision socket and a Leatherman-standard socket, and the Extreme's 1/4″ socket has a lock so the bit stays with the card instead of with the screw. The Bit Store Card is the magazine for all of them: eight double-sided bits — sixteen tips — held in rubber rings, plus three built-in drivers (1/4″ hex, 1/8″ flat, 4 mm precision).
The Universal cards also carry a modular slot, and the inserts that go into it turn the same card into pliers or a wrench set. They click in and twist out with no tools, no screws and no rings holding them — sprung tongues do the work. If your card has the slot, learn it early: it is the difference between one tool and a small system.
05 · MEASURINGMeasuring and drawing: rulers, gauges, angles
Every card carries rulers on the edges, metric on one side and imperial on the other — the Universal 3.0, for example, reads 0–60 mm and 0–2″. Lay the edge on the work, read at eye level, and remember that a card ruler is a field instrument: it is honest to a millimetre, not to a tenth.
The gauges are the part people underuse. A drill guide is a row of holes, not a scale: the drill either passes through the Ø4.2 hole or it does not, and that go/no-go answer beats any amount of squinting at a rule. The same logic runs the sheet thickness gauge, the tyre tread depth gauge and the wire holes. The Universal 4.0 and 5.0 carry metric and imperial drill guides plus a sheet gauge; the Professional carries the full set on both measuring systems, along with a precision protractor, a plumb scale, a circle template and a phone stand.
For drawing rather than checking, the Designer is the specialist: 87 × 54 × 1.5 mm of anodised 6061 aluminium at about 17 grams, with circle templates, arcs, protractors including a radian scale, L-squares, quick angles at 30, 45 and 60 degrees, isometric grids and a parallel-line guide. It has no blade and no point, which is the reason it lives in a laptop sleeve and clears every scanner. Both drafting cards are 1.5 mm thin on purpose — a drafting edge wants to sit flat on paper, not stand off it.
06 · OPENERSOpeners and everyday jobs
The bottle opener is the tool that gets used most and respected least. Hook the lip of the cap in the notch, let the shoulder of the cutout rest on the crown, and rotate the card around that contact point — the card is the lever, your wrist is the pivot, and the cap comes off without bending anything. Nearly every card has one: the whole Universal series, the Extreme, the Adventur, the OfficeWorker, the Professional, the Lumberjack, the Pocket Tool and the S Keychain. The Bushcrafter, the Designer and the Survival Wallet Kit do not — worth knowing before you buy for that reason.
The box opener is a recessed hook that catches packing tape and parcel strap without exposing an edge you can cut yourself on; on the Universal 4.0 there is also a scoring tool for cardboard you want folded rather than opened. Beside them sit the small everyday shapes: a can opener, a scraper for labels and grill grates, a cord cutter for thread, zip ties and blister packs, a nail puller, a pry tip and a wire stripper. None of them is exciting. All of them are the reason the card leaves the wallet on an ordinary Tuesday.
If those jobs are the whole of your day, the OfficeWorker is the card built around them: 40+ tools, 22 numbered cutouts, 2 mm, and zero blades by design — rulers, squares, small hex nuts, a Phillips in the plate, an opener, a cord cutter, a pry tip. It is the card that goes through a lobby scanner without a conversation.
07 · CUTTING EDGESCutting edges — and where they are legal
Four cards carry a real edge. The Universal 3.0 has a knife and a survival axe; the Universal 5.0 has a sharp knife, a sharp hatchet and a serrated section; the Adventur has a knife and an axe on 3 mm of plate; the Bushcrafter has a knife, an axe and saw teeth along the bottom edge. The Universal 4.0 deliberately does not: it keeps a shovel corner and a semi-sharp hatchet edge — a scraper you can put an edge on with a stone if you ever have to — plus a knife sharpener, and gives up the firestarter and the sharp axe of the 3.0. The Extreme has a recessed cord cutter and no blade at all. The OfficeWorker, Professional and Designer have nothing to sharpen.
Legality is not a footnote, it is the deciding factor for many buyers.
Technique is short because the geometry is short. Cut away from yourself with a draw stroke, keep the card flat in the cut, and use the corner nearest your grip for control. Serrations saw rope, webbing and cord honestly; they are not a wood saw, and the plate will tell you so before the branch does. For wood, the method is a hatchet edge and a baton — the physics of that, in joules, is a whole article of its own.
Legality is not a footnote, it is the deciding factor for many buyers. An edge on board changes where the card may travel: in the UK the reference is Section 139, in Germany §42a, in France the Category D framework — and at an airport, an edge means checked luggage while the blade-free cards are built for the cabin. The plain-language map is in the legal article, and the airport-specific version is in the TSA one.
If cutting is the main job rather than the occasional one, the honest answer is a folding knife next to the card, not a thicker card. That is what the MRF Fold is for — the same milled logic taken to a folder, with a lock built out of sprung tines rather than a spring.
08 · NAVIGATIONNavigation instruments on a flat plate
The sundial is the instrument people find hardest to believe and easiest to use. Stand a match or a twig in the centre hole, hold the card dead level, and the shadow becomes an hour hand: the sun moves a steady 15° per hour, so the dial reads time directly. The Universal 3.0, 4.0 and 5.0 fold the twelve-hour sweep into a 90° fan read in two grips, each with its own arrow; the Adventur and Bushcrafter carry the full 180° fan and need no turning. Run it the other way — set the known time, and the shadow gives you the direction instead.
At night the instrument changes. The parallel guide on the Universal 4.0 and 5.0, plus a thread and any nut, makes a quadrant: the altitude of Polaris above the horizon equals your latitude, and one degree of sighting error costs about seventeen metres of drift per kilometre walked. The moon phase calendar — which is on the Universal 4.0 only, not on the 3.0 and not on the 5.0 — tells you how much light you will have and when, which matters more on a night march than any romantic reading of it.
Two things to keep honest. A sundial compass is a field instrument, not a GPS: it wants a level card and a clean shadow, and its accuracy improves substantially once you apply the standard corrections — the sundial article walks through them. And the OfficeWorker carries only a compass hole, not the full dial, because it was built for a different environment. The fastest way to learn any of this is the trainers: they run the instrument on screen before you ever hold one.
Run it the other way — set the known time, and the shadow gives you the direction instead.
09 · FIRE & SURVIVALFire, cordage and the shovel corner
A ferro rod does not light anything by itself — it sheds burning metal when you scrape it, and the scraping edge must be square, not sharp. That is why the firestarter on a card is a separate 90° scraper and not the knife edge: press hard, push slowly, and you get a shower of hot sparks into the tinder instead of a fast scratch and nothing. The Bushcrafter carries a replaceable ferro rod held in a rubber ring; the Universal 3.0, the Universal 5.0 and the Extreme carry the scraper geometry on the plate.
Around the fire the same card does the boring work: serrations for cordage and webbing, a line winder on the Bushcrafter, and the shovel corner — present on the Universal 3.0, 4.0 and 5.0, the Adventur and the Bushcrafter — for a fire pit, a drainage channel or a cat hole. Think trowel, not spade: you are moving forest floor and loose soil with a 55 mm blade, so dig with short strokes and let the corner do the cutting.
If the survival case is the whole reason you are here, there are two different answers. The Bushcrafter is one dense card — twelve survival tools, 2.4 mm, about 52 grams, ferro rod, saw teeth, knife, axe, sun compass. The Survival Wallet Kit is the opposite philosophy: three 0.8 mm stainless cards holding 31 removable tools split into Fisherman, Hunter and Urban sets, which travels in checked luggage and is meant to be used up rather than kept pristine.
10 · WHICH CARDWhich card is yours
Ten cards make up the series. They are not ten versions of the same idea: each one gives something up to be good at something else, and the two questions that separate them are whether it carries an edge and how much it weighs in your pocket.
Three of them — the Universal 5.0, the Bushcrafter and the OfficeWorker — are the ones people most often buy for the wrong reason, so run the Card Finder first if you are between two of them.
11 · CARRY & CARECarry, care and travel
A card carried loose in a pocket with keys and coins will work fine and look worn in a month — the etched scales are the first thing to polish away, and those scales are half the tool. Two holders solve it. The MRF Wallet is a full-grain leather cardholder with three compartments and an elastic tool band, sized to take any of our cards plus a folder, a pen or a pry bar. The Leather Sleeve is the minimal version: hand-cut, double-stitched, 2.5 mm, made to fit the Universal 3.0 and 4.0, the Adventur, the Designer and the Professional alongside your bank cards.
Care takes a minute a month. Hardened 440C is stainless, not rust-proof: after sweat, salt water or a wet day, wipe it dry and leave the thinnest film of oil on it. Titanium ignores all of that and needs nothing but a wipe. Anodised aluminium — the Designer — keeps its colour as long as you keep abrasives away from it; use soap and water, not a scouring pad. If an edge dulls, the sharpening angle guide on the Universal 4.0 and 5.0 gives you the angle to hold against a stone.
For travel the checklist is short. A card with an edge goes in the hold, every time. A blade-free card rides in the wallet in the cabin, and it helps to put the whole wallet in the tray rather than leave a metal plate in a jacket you are about to throw in a bin. If your Universal is wearing a KIT insert with a blade in it, take the insert out and pack it in the hold — the card itself stays with you. And whatever the spec sheet says, the officer in front of you decides on the day.
A card with an edge goes in the hold, every time.
12 · FAQQuestions people actually ask
What is a credit card multitool? +
A flat plate the size of a bank card — 85 by 55 mm on most of our cards, 87 by 54 mm on the drafting ones — with tool shapes cut through it. Depending on the model it is 1.5 to 3 mm thick and carries from a dozen jobs to more than eighty. It is not a folding multitool with a smaller waist: nothing moves, nothing unfolds, and every tool is a shape in one piece of metal.
How do I know which cutout does what? +
Every functional cutout is numbered on the plate. The numbers are an index, not decoration: open the Tool Explorer, spin the same card in 3D, tap the number and read what the shape is for. Between 22 and 57 numbers are marked, depending on the model. Open the Tool Explorer →
Can I take a card multitool through airport security? +
A card with no blade — Universal 4.0, Extreme, OfficeWorker, Professional, Designer, Bit Store Card — is designed to clear hand luggage, and the spec plate on each of those says so. A card with an edge on board — Universal 3.0, Universal 5.0, Adventur, Bushcrafter — travels in checked luggage. The standing rule at every checkpoint still applies: the officer's discretion outranks any spec sheet. Full airport guide →
Can a flat card really turn a bolt? +
Yes, inside its limits. The card gives you about 50 mm of arm, which is enough for a bike bolt, a saddle clamp, a furniture nut or a gas fitting, and not enough for a wheel nut. The Extreme's torque handle, which comes with the Full Kit, roughly triples the leverage. A rounded or seized fastener is a job for a socket, not for a card.
Does the card have a Phillips screwdriver? +
Cut into the plate itself — on the Universal 5.0, the Extreme and the OfficeWorker. On the Universal 3.0, Universal 4.0 and Adventur, cross-head screws are driven through the bit driver with a bit, not by the plate.
Which card has the moon phase calendar? +
Only the Universal 4.0. It is not on the 3.0 and not on the 5.0. The sundial clock and sundial compass are wider spread: Universal 3.0, 4.0 and 5.0, Adventur and Bushcrafter all carry them, and the OfficeWorker carries a compass hole. What the dial predicts →
Is the serrated edge a saw? +
It saws rope, webbing and cord, and it is honest work on those. It is not a wood saw — the teeth are short, the plate is thin, and a branch will win. Anything thicker than your thumb is a job for the hatchet edge and a baton, not for the serrations.
Does every card have a bottle opener? +
Almost. The Universal series, Extreme, Adventur, OfficeWorker, Professional, Lumberjack, Pocket Tool and S Keychain all have one. The Bushcrafter, the Designer and the Survival Wallet Kit do not — the first two spend their millimetres on other jobs, and the third is a set of removable tools rather than a plate.
Titanium or steel? +
Grade 5 titanium runs 35–37 HRC and roughly half the weight; hardened 440C runs 52–54 HRC and holds an edge and a wrench flat better. Titanium is the wallet answer, 440C is the workbench answer. The full comparison, with the numbers behind it, is in the materials article. Titanium vs 440C →
What if the card I picked turns out to be the wrong one? +
Take the Card Finder before you order — four questions, about 30 seconds, and it matches a card to how you actually carry rather than to how the catalogue is sorted. If it still misses, there is a 60-day guarantee on the order. Take the Card Finder →
Andrii Gurskyi, founder & engineer, MRF.Tools
In 2015 he went looking for a real tool for his own wallet, found only stamped junk or overpriced steel — and started machining his own. Ten funded Kickstarter campaigns, 4,000+ backers, every reward shipped — several of them through a war. Designed and developed in Ukraine. About MRF →