Given a travel related situation, and given a specific question about the situation, summarize the question into a title

Q: I see many questions here refer to a US "visa stamp", or "getting a visa stamped" for the US, and I often find it difficult to imagine what is going on with this stamp.

Is it the visa sticker itself that is being referred to as a "stamp"? (This wouldn't be quite as crazy as it sounds -- a postage stamp is a sticker, after all -- but on the other hand such a usage is not evident for any other country's visa stickers).
Or is it the admission stamp in one's passport (showing immigration category and how long a stay one has been granted) that people call a "visa stamp", despite not actually being a visa?
Or do (some classes of?) US visas actually need to have some kind of ink stamp applied to them in order to be valid?

A: What's the deal with "stamping" US visas?
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Q: I always thought that the point of "checking in" to a flight was so that the airline knew you were at the airport and would most likely board the plane.

But nowadays you can check in by computer or smartphone, which is great -- but you can do so as much as 24 hours before the flight. That's before you even go to bed the night before the flight, let alone arrive at the airport.

If there's a emergency, or even very bad traffic, that makes you miss your flight, won't it be in the last few hours? What good is checking in so far in advance?

EDIT: And almost as soon as I finished typing my question, I saw this: What is the purpose of check-in before flying?

A: Why can you check in to a flight the previous day?
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Q: Wiki gives us the following explanation of the use of high beams in a car:

Main-beam (also called high, driving, or full beam) headlamps provide an intense, centre-weighted distribution of light with no particular control of glare. Therefore, they are only suitable for use when alone on the road, as the glare they produce will dazzle other drivers.

But what if you drive at night on a fully separated highway, such as the Autobahn? Are you allowed to turn on the high beams? I assume the middle barrier will prevent other drivers from getting blinded, but perhaps it would also be annoying to the drivers in the front?

A:
Is it legal to turn high beams on when driving on a European highway with fully separated lanes?
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