Different mapmakers use different symbols for roads, railways, towns, or any of the hundreds of things maps are used to show. A country road might be yellow on one map, green on another or gray on another. Also there are special maps for mariners and aviators called charts, special maps for geologists, foresters, hikers and campers, vehicle drivers and so on. This great variety is confusing to the person using the map. Hills may be shown by tiny pictures of hills; by shading the map to show the hills as if they cast shadows; using lines that join points of equal height called 'contours'; or simply a dot with a number to show the height. To help those using the chart or map so that they can see what the real countryside might look like, the mapmaker places the symbols or signs used in a box on the map and names the box KEY or LEGEND. The key above is relevant to the island maps.