Day 4...Letterbox

Let me tell you a secret: Today, I typed "letterbox" into Google. It just felt like one of those words whose definition I was pretty sure I knew but I thought I'd just do a quick check to make sure. Suffice it to say that I was surprised at how many things are referred to as "letterbox"! Seriously, look it up ( <-- go on, click it). There's the film consideration, the stamp hobby, the synonym for mailbox... Too many things to think about! Whew, geez. But I suppose I should do them all their deserved justice so in order we have:

1. Letterbox (filming): I like being able to see a lot more of the surrounding background when watching movies/TV so the wider/shorter combination actually sounds nice to me.
2. Letterbox (the stamp hobby): Even after researching it for a bit, I'm confused. Is it making stamps? Is it putting cool stamps in cool books? Puzzle solving plays into it how? Please, someone explain. It sounds the tiniest bit like geocaching? Is it geocaching's stamp-fanatic cousin?
3. Letterbox (synonym for mailbox): Mine is empty today. I thought about taking a picture of it for this but then work got crazy and I couldn't. :( I got a letter from my Grandma and a gift card from my mom the other day, both of which were wonderful. I sometimes have mail from my penpals but they've all been busy recently. Speaking of, I need to give all of them an address they can send things to over the summer. 
• Super exciting side note: in a week, I will be off campus and out for the summer! Can't believe I'm that close to being done with sophomore year :)