Letterboxing is an outdoor hobby that combines elements of orienteering, art, and puzzle solving. Letterboxers hide small, weatherproof boxes in publicly-accessible places (like parks) and distribute clues to finding the box in printed catalogs, on one of several web sites, or by word of mouth. Individual letterboxes usually contain a notebook and a rubber stamp. Finders make an imprint of the letterbox's stamp, either on their personal notebook or on a postcard, and leave an impression of their personal stamp on the letterbox's "visitors' book" or "logbook" — as proof of having found the box and letting subsequent letterboxers see who have visited. Many letterboxers keep careful track of their "find count".
Evidently, it originated in England and first gained popularity in the United States after a 1998 article in the Smithsonian. There seem to be two kinds of letterboxers; ones who want to keep it "underground" and ones who are happy to tell you about it. I found out about it from a friend who goes out with her kids.
I carved my own stamp and created a kit to take with us on outings which contains the stamp, several inkpads, my journal and a pen...and all in a handy quart size ziploc bag (just like I'm taking it on a plane. :) As my kids are not really interested in anything crafty, they don't have their own log books and stamps, but we go out as a family. If they show interest, I'll set them up too.
This is a not very good picture of the imprint of my stamp. My trail name is "Civetta" which is Italian for owl. (I'm probably not supposed to share all that). I took a photo of a cool owl candle I have in my home. I edited it to be high contrast and set the dimensions as I wanted them, then printed it in black and white and transferred the image to the carving material, then carved it in. The "Civetta" is freehand. This was a partial evening project, start to finish.
I checked out this book from the library which gives a good overview and stamp carving instructions. I was able to put my kit together for less than twenty dollars and carving the stamp was easier than I thought it would be. I have enough leftover carving medium to make three more stamps. I think a lot of hardcore letterboxers carve their stamp "on site".
One of the cool benefits of this hobby is that our little hiking outings and nature walks can have another layer of fun and purpose and we will go to different spots that we may not have gone to without this impetus. We can also search for letterboxes while on trips.
I've already chosen the spot where I am going to plant my own box this summer. So I guess this makes me the kind of letterboxer that's happy to tell you about it.... ;)