With its roots in Dartmoor in England, Letterboxing involves a waterproof box hidden in a scenic location and containing a rubber stamp and notebook; a person uses a series of clues (some are more cryptic than others) and possibly a compass and map to search for a box. Once found, the finder will stamp the box's notebook with his or her personal stamp, and use the box's stamp to mark their own personal notebook. Letterboxers collect the stamps from boxes all over the world. Similar in some ways to geocaching.
"I just got a patch for collecting my first hundred letterboxes!"
Hiding a box in a remote location and giving clues on how to find it. Inside the box is a notebook and a stamp. Serchers bring their own stamp and book; they use their stamp to mark the book in the letter box. They then use the stamp in the box for a mark their notebook.
The letter boxing clues made the hidden box easy to find.