hunters, or trails descended from those routes. Originally a tree would be blazed by hatchet chops (still the dictionary definition) but today other methods have become more common, with environmental and aesthetic concerns sometimes playing a part in the choice of blazing method. Other navigational aids, such as cairns, are used where blazes are unsuitable. In 1902 the miners of Idaho created and marked the Three Blaze "shortcut" Trail with a series of three distinctive blazes cut on the trees, usually with an axe, to define the specific route to the Thunder Mountain Mines of Central Idaho. Affixed markers Alternatively, more long lasting plastic, metal or even sometimes wooden markers may be affixed to trees, usually with nails. The placement of these markers requires more skill and labor than paint, as well as an area with an abundant supply of trees to which to attach them. Flagging Surveyor's tape hung from branches or tied around trees is sometimes used to indicate trail routes, but usually only for temporary or unofficial trails, most commonly when a trail route has been selected but the trail itself is under construction. Flags are sometimes used for permanent trails, but they are the most vulnerable to the elements of any trail blazing method and may be more difficult to see. Trail flagging is the predominant method to mark a mountain hiking trail in Japan. Red ribbons usually indicate an ascent route while yellow ribbon indicate a descent route. On some mountains, a non-standard ribbon colour (white or blue) is used to identify a specific trail. Poles Poles, colored or not, are often used to keep the trail visible during winter and under snow cover. Poles are standard trail markers in Austria, Canada, USA, the Czech Republic, Switzerland, and Slovakia. Cairns Cairns are carefully arranged piles of stones. Cairns are most commonly used to indicate trails in open areas, such as higher-elevation alpine areas, where no trees are available, or where conditions may make blazes hard to see. An ancient example is the inuksuk (plural inuksuit), used by the Inuit, Inupiat, Kalaallit, Yupik, and other peoples of the Arctic region of North America. These structures are found from Alaska to Greenland. This region, above the Arctic Circle, is dominated by the tundra biome and has areas with few natural landmarks. Below the tree line, cairns are used less frequently, often like flagging to indicate informal or