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What Are Those Dark-Green Mailboxes That Don't Accept Mail?

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You know a mailbox when you see one. (They’re those blue hunks of metal bolted to the sidewalk with the creaky flaps that go reeeeaaaaaallllk when you pull them open.) But what about the dark-green boxes that don’t have any slots to accept mail?

Called postal relay boxes, these work as storage containers for mail carriers as they make their rounds. Carriers can replenish their bags on the go, removing the need to constantly return to the distribution center (or carry everything at once). They are most prevalent in cities where USPS workers make deliveries on foot, and the boxes are either filled by the carriers themselves or postal workers in trucks who make larger delivery runs.

Ideally, these relay boxes are put at the most convenient possible locations along carriers’ routes. A 1992 study in the American Journal of Mathematical and Management Sciences titled “Locating Postal Relay Boxes Using a Set Covering Algorithm” [PDF] details the number-crunching that goes into this. Using data from Canadian mail routes, the researchers took into account things like maximum mailbag weight (35 pounds), average mail volume (depending on day), and the number of mail carriers who can use each relay box at once. The algorithm resulted in a lower number of needed relay boxes, which cut down on cost.

You may have noticed that a green relay box that was present on your corner, say, ten years ago may no longer be there. As the Internet further reduces the need for paper mail, carrier loads have been getting lighter, accounting for fewer relay boxes. When Gothamist asked a USPS representative about the disappearing boxes, they confirmed that they were being removed “if they were no longer needed.” The rep was also tight-lipped about the very nature of the relay boxes, telling Gothamist’s Jen Carlson, “[They] are for official postal use only. Any further information regarding them is proprietary."

This reticence was likely due to security concerns. According to the Postal Inspection Service’s law enforcement guide, “relay boxes can contain large quantities of mail in gray sacks that thieves cart off looking for checks and credit cards.” It goes without saying, but please leave the relay boxes alone; they're just trying to help.

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Big Questions
What Are Curlers Yelling About?
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WANG ZHAO/AFP/Getty Images

Curling is a sport that prides itself on civility—in fact, one of its key tenets is known as the “Spirit of Curling,” a term that illustrates the respect that the athletes have for both their own teammates and their opponents. But if you’re one of the millions of people who get absorbed by the sport once every four years, you probably noticed one quirk that is decidedly uncivilized: the yelling.

Watch any curling match and you’ll hear skips—or captains—on both sides barking and shouting as the 42-pound stone rumbles down the ice. This isn’t trash talk; it’s strategy. And, of course, curlers have their own jargon, so while their screams won’t make a whole lot of sense to the uninitiated, they could decide whether or not a team will have a spot on the podium once these Olympics are over.

For instance, when you hear a skip shouting “Whoa!” it means he or she needs their teammates to stop sweeping. Shouting “Hard!” means the others need to start sweeping faster. If that’s still not getting the job done, yelling “Hurry hard!” will likely drive the point home: pick up the intensity and sweep with downward pressure. A "Clean!" yell means put a brush on the ice but apply no pressure. This will clear the ice so the stone can glide more easily.

There's no regulation for the shouts, though—curler Erika Brown says she shouts “Right off!” and “Whoa!” to get her teammates to stop sweeping. And when it's time for the team to start sweeping, you might hear "Yes!" or "Sweep!" or "Get on it!" The actual terminology isn't as important as how the phrase is shouted. Curling is a sport predicated on feel, and it’s often the volume and urgency in the skip’s voice (and what shade of red they’re turning) that’s the most important aspect of the shouting.

If you need any more reason to make curling your favorite winter sport, once all that yelling is over and a winner is declared, it's not uncommon for both teams to go out for a round of drinks afterwards (with the winners picking up the tab, obviously). Find out how you can pick up a brush and learn the ins and outs of curling with our beginner's guide.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Why You Should Never Take Your Shoes Off On an Airplane
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What should be worn during takeoff?

Tony Luna:

If you are a frequent flyer, you may often notice that some passengers like to kick off their shoes the moment they've settled down into their seats.

As an ex-flight attendant, I'm here to tell you that it is a dangerous thing to do. Why?

Besides stinking up the whole cabin, footwear is essential during an airplane emergency, even though it is not part of the flight safety information.

During an emergency, all sorts of debris and unpleasant ground surfaces will block your way toward the exit, as well as outside the aircraft. If your feet aren't properly covered, you'll have a hard time making your way to safety.

Imagine destroying your bare feet as you run down the aisle covered with broken glass, fires, and metal shards. Kind of like John McClane in Die Hard, but worse. Ouch!

Bruce Willis stars in 'Die Hard' (1988)
20th Century Fox Home Entertainment

A mere couple of seconds delay during an emergency evacuation can be a matter of life and death, especially in an enclosed environment. Not to mention the entire aircraft will likely be engulfed in panic and chaos.

So, the next time you go on a plane trip, please keep your shoes on during takeoff, even if it is uncomfortable.

You can slip on a pair of bathroom slippers if you really need to let your toes breathe. They're pretty useless in a real emergency evacuation, but at least they're better than going barefoot.

This post originally appeared on Quora. Click here to view.

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