The Formula One wheel gun: It’s a simple piece of technology, and yet it’s responsible for some of the biggest triumphs and failures in the sport. Today, we’re going to let Mercedes walk you through the way these wheel guns work—and why, sometimes, they don’t.

Mercedes made this video in direct response to the sheer number of people that demanded to know what the hell happened during the team’s pit stop at the . I can appreciate the team’s sense of humor about the very awful situation. I can also appreciate that they used it as an opportunity to demystify the whole Formula One scene with some good old fashioned education.

(Welcome to , the series where we break down racing rules and concepts in easily digestible ways for all the beginners out there. If there’s something you’ve always wondered about or something that has never made sense, leave your topic in the comments or email me at .)

Without further ado, let’s turn it over to Aaron Jeeves, a left front end mechanic at Mercedes for Valtteri Bottas’ car:

The tool, called the Super Gun 3, looks like the kind of thing you’d see on a laser tag field. It’s a pneumatic tool operated with compressed air, so that when you pull the trigger, the gun will either tighten or loosen the wheel nut. Because this is F1, the guns are designed to avoid the millisecond it would take a mechanic to flip a directional switch. So, the first time you pull the trigger, it automatically loosens the wheel nut. The next time you pull it, it automatically tightens.

That right there is problem number one: if a mechanic struggles to, say, tighten the wheel nut, he’ll have to pull the trigger twice instead of once to get that wheel back on during a stop. That’s a rarity, considering how well-trained pit crews are, but when it happens, it is a very bad time. Look no further than this year to tell you how a bad stop can go.

Crew members are trained to minimize movement during a stop, since any unnecessary movement wastes time. So, crew members are ready and waiting in position when a driver brings in the car, at which point they really only have to push their arm forward an inch or so to start taking off the tire. Part of a wheel gun’s functioning well is the crew member being within arm’s reach of the car. There’s also a spare wheel gun available during stops if one fails.

The wheel guns are also electronically connected to a pit gantry that collects all the data from the stop. Once a mechanic has successfully completed a stop, he presses a button that lets the team know he’s done. When all four corners of the car have been changed and confirmed, the driver can head off.

Still looking for the nitty-gritty details? We’ve got ‘em.

High-powered wheel guns really became important after F1 banned refueling. In the past, it didn’t really matter how long it took to change tires during a pit stop, since refueling the car inevitably took a little longer. But after refueling was banned in 1994, quick tire swaps became crucial to having a quick pit stop overall. You needed to change the tire quickly, you needed to do it right, and you only had one chance to do it.

Back in the day, F1 mechanics used to hammer the tire onto the wheel hub. Eventually, technology allowed them to move on to pneumatic wheel guns crafted either by the team itself or by .

Modern F1 wheel nuts look nothing like wheel nuts did in the past. The nut is made of weird sockets and fins that are designed to precisely lock the tire into place. So, when you put a tire onto the axle, it perfectly fits onto the drive pins without requiring you to wiggle the tire around. The nut must be locked into place on the tire, as per FIA standards, to prevent it from flying off willy-nilly.

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The wheel gun socket pushes the pins into the axle to allow the nut to be removed. When refitted the nut passes over the pins and they spring out when the nut is nearly fully seated and gun removed. With this system, it’s not until the wheel gun socket is pulled from the axle that the mechanic can visually confirm the nut is on and the retention mechanism is in place. Often we see mechanics signal their job is done and then frantically wave amid the realization that the nut is not in fact fitted correctly.

The wheel gun can actually kind of a pain in the ass if you aren’t careful with it. This thing can produce over 3000 Newton-meters of torque (2212.686ft-lb) and around 9000 rpm, so it can easily destroy the precise etchings on the wheel nut. This seems to be the problem that Ferrari has had in 2020; the gun ends up stripping the nut because of the sheer amount of force and possibly an awkward fit between gun and nut.

And, like most things in F1, this equipment is expensive. One of McLaren’s used wheel guns from 2018 is , and new ones go for about that, too. All that to shave a few milliseconds from a pit stop time.