Swiss Army Knives Are Agile

Every discipline and every niche has a “Swiss Army knife of X”. Why are they so prevalent, and what makes them so valuable to engineers and software developers?

In the summer of 2003, I acquired my first truly useful Swiss Army knife. I had been working my first term as an electrical engineering co-op on the floor of an automotive aluminum foundry. The facility was highly automated, particularly by foundry standards, and one of our suppliers, Güdel, one day brought branded Classic SD pocket knives in as promotional swag. My supervisor tossed one across the office to me, and it became one of a few lasting impacts he had on my life: two decades later, I still carry one with me everywhere I go (though I’m on my fourth or fifth now, thanks to encounters with airport regulations and nightclub bouncers over the years).

The Classic SD is a small knife, 58 millimeters long and weighing 21 grams. It has seven tools: a blade, a screwdriver and nail file, scissors, tweezers, a toothpick, and a key ring. These tools turn out to be quite versatile in everyday life, which is, of course, the point: by design, a Swiss Army knife aims to optimize its ratio of usefulness to compactness and convenience.

Apart from the Victorinox (and erstwhile Wenger) offerings, Swiss Army knives, in the generic, abound across a wide swath of modern human technology. Obviously comparable are other multitools a la Gerber or Leatherman, along with more specialized designs for such niches as camping. My favourite corkscrew design, for example, is the Pulltap, which incorporates a bottle opener and a serrated knife blade: everything you need to open bottles, in a single sleek tool. But the label has proliferated in high tech as well: in electronics, it’s been applied to the multimeter, and as of writing, a search on GitHub turns up 1,280 software applications and libraries billing themselves as the Swiss Army knife of some or other thing.

In March of 2020, I backed an interesting project on Kickstarter: the Flipper Zero. The Flipper is what you might call a Swiss Army knife for real-life digital systems. Its interfaces include RFID/NFC, sub-gigahertz radio, infrared, iButton (Dallas 1-wire keys), USB, and 3.3V GPIO, with the last enabling custom add-on modules for other interfaces such as wi-fi. On board are a variety of standard applications for capturing, analyzing, cloning, and emulating signals and devices, among other useful tools, and the open-source firmware allows users to create and run custom applications.

During the Kickstarter campaign, critics pointed out that the Flipper Zero brought nothing particularly new to the table: that such existing products as the Proxmark3 and the HackRF One provided superior capabilities, at least from a strictly tech-spec perspective, in relatively affordable and portable form.

I submit that the Flipper’s immense popularity in spite of these criticisms comes down to the Swiss Army knife design objective: no other device on the market offered such a versatile tool set, useful in everyday scenarios, in such a compact and convenient form factor. Like my Classic SD, the Flipper Zero is the sort of tool that’s sufficiently small (100 millimeters, 104 grams) and convenient (5-9 day battery life and a self-contained, user-friendly UI) that it’s worth carrying around with me most of the time, just in case it might be useful in some unexpected situation.

So what do I actually do with it? One feature that sees a lot of use is the infrared tool: armed with the Flipper-IRDB database, of which I am a maintainer, a great many devices I encounter are under my control. That’s handy when the remote is misplaced at a friend’s house, and reducing the AV pollution from a proliferation of unwatched televisions at the pub can, in my humble opinion, be considered a community service. The RFID and NFC tools are always at hand to clone access cards for hotel rooms and apartment buildings sans the hassle of official channels (this may have saved me from missing a train in Hamburg once, when no one was around to give me the keycard to spring my stashed luggage). I use the sub-GHz radio to control my back-yard outlets, the dance floor lighting at a local venue during my shows, and Tesla charging ports everywhere (as a party trick). Since I often have it with me anyway, I also use the USB U2F feature for authentication into some of my online apps. And finally, as an electronics hobbyist, I’ve used the GPIO pins and UART bridge as a quick interface to my projects countless times. Look forward to future posts on this blog detailing some of my learning projects involving the Flipper!

Whether the interfaces to the world are physical things, electronic signals, software APIs, or something else entirely, the key design principle of a Swiss Army knife is the same: to be as compact and convenient as possible, while offering the most utility across a broad set of potential scenarios. In the parlance of axiomatic design, these functional requirements are highly coupled and often in direct opposition, so it’s a bit of an art to design a good product like the Classic SD or the Flipper Zero. But the payoff is clear: a tool that meets some of your needs that you have with you all of the time is going to see a lot more use than a tool (or a set of tools) that meets all of your needs but that you only rarely have at hand.