"The low elevation of the [Marshall Islands] and the distances between the atolls make them particularly difficult to sight from the sea. In travels between islands, early inhabitants learned to read the patterns of the waves by watching for swells which would show when land was ahead.
"Stick charts were used to teach the secrets of navigation. They were made by tying flat strips of wood together in designs which imitated the wave patterns. Shells were then attached to these sticks to represent the islands.
"Three kinds of charts were used. The _mattang_ showed wave patterns around a single island or atoll and was used first to teach the basic techniques. The _medo_ showed patterns around a small group of atolls and the _rebilit_ mapped an entire chain, showing the relationships between the islands and the major ocean swells.
"All the information contained on the stick charts was memorised and the charts themselves were not actually taken on journeys. Not many present-day Marshallese understand how to read stick charts, though due to their popularity as souvenirs many islanders can still make them."