Players begin with the clues, usually found on the Internet. When these are decoded, the player hikes out to discover the site of the hidden letterbox. To prove that they have both solved the puzzle and made the trek, a rubberstamp is stowed away in the letterbox.
Successful players can impress the coveted stamp into their journal.
According to legend, in 1854 a Victorian gentlemen hiker put his calling card in a bottle and stuck it into a bank at Cranmere Pool, in a remote part of Dartmoor in southwestern England. Visitors from around the globe prowl the heath at Dartmoor in search of the elusive boxes and the artful stamps inside. In April of 1998, Smithsonian magazine published an article on the Dartmoor letterboxes. With the Internet as a primary means of communication, the idea soon spread around the country. Web-sites and a discussion group were established.