Driveby caches with places to stop.
Letterbox Caches
The letterbox contains a logbook, and a ink stamp. When cachers find the container, they stamp the logbook with their personal stamp, and also stamp their own notebook with the stamp from the letterbox, as a souvenir of their visit.
In geocaching, cachers can treat letterbox geocaches just like a traditional geocache, and the stamping element is not mandatory. But having your own personal 'stamp collection' is part of the fun so if you have a stampbook of your own and a personal stamp, please remember to bring it along, to give you something to remember the cache by.