Trail blazing, or trailblazing, is the practice of marking paths in outdoor recreational areas with blazes, markings that follow each other at certain — though not necessarily exactly defined — distances and mark the direction of the trail. In older times, a tree could be blazed by hatchet chops, while today other methods have become more common, with environmental and aesthetic concerns sometimes playing a part in the choice of blazing method.
Types of blaze 
In modern times, most commonly, a painted marking of a consistent shape or shapes (often rectangular), dimension and colour or combination of colours is used along the trail route. The system by which blazes are used to signify turns and endpoints in trails (see below) strongly favors the use of paint blazes. Commonly, in North America, to avoid confusion, it is one single colour, often white, red, blue or yellow. Other trails, especially in Europe, may use more complex systems of painted shapes in more than one colour. Some Austrian trails, for example, use a combination of white and coloured stripes, while Middle European countries such as Czech Republic, Slovak Republic and Poland use coloured bars with different meanings attached to different colours. Trails in Africa are often marked by yellow footprints painted on trees and rocks.
When using paint on trees, the preferred technique is to use a drawknife to smooth the outer bark of trees without penetrating to the inner bark (so as to not injure the tree), then using an oil-based paint to create the blaze. Since paint introduces small amounts of potentially toxic chemicals into a protected environment, it is often preferred to keep the blazes small. Stencils are often useful, and sash brushes are the preferred brush type for precise work. Oil-based paint seems to last longer than latex-based and seems to be more benign to the bark. Blazes may also be painted on obvious rock surfaces or on posts set into the ground (or on utility poles, fences, or other handy surfaces) where the trail follows a road or goes through fields and meadows.
Affixed markers 
Alternatively, plastic, metal or even sometimes wooden markers may be affixed to trees, usually by nails. These last longer than paint, but are vulnerable to both the chewing of animals (porcupines especially) and the growth of the tree swallowing the nails and causing the marker to fall off. To protect against this possibility, most markers are put on nails with some space between the head and the bark. The placement of markers requires more skill and labor than paint, as well as an area with an abundant supply of trees to which to attach them.
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. They 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.
Cairns, also called "ducks," are carefully arranged piles of stones, and are most commonly used to indicate trails in open areas, such as higher-elevation alpine areas, where no trees are available and painting on rocks is often done but either would not last or are not always easy to see. In the Presidential Range of New Hampshire's White Mountains, for example, cairns are found at ten-foot (three-meter) intervals along trails above treeline, so that hikers forced to crawl by heavy winds and occasional infamously lethal weather can find their way to safety.
Below treeline, cairns are used less frequently, often like flagging to indicate informal or unofficial paths or just their junctions with official trails. They are the least visually intrusive and most environmentally friendly blazing method. However, their construction requires sufficient stones be either available in the area or brought to the trail. They may become obscured by snow in areas with heavy winters and may be easily knocked over.
Lastly there are trails blazed by cuts made in bark by axe or knife, usually the former. Most often these are informal routes made by loggers or hunters, or trails descended from those routes. Due to the maintenance and skill required, as well as an increasing aversion to harming trees, this method is almost never used today, although in past centuries it was often the only method used.
The amount of blazing used on a trail is often impacted by different land-management principles, as well as the kind of users the trail is likely to get and what kind of trail it is in the first place. In U.S. wilderness areas, whether state or federal, the U.S. Wilderness Act requires that the land seems "untrammeled by man," and so blazes are often kept to a minimum. Most wilderness trails are also used by serious hikers and backpackers who may find excessive blazing to be visually annoying or distracting.
By contrast, in a typical municipal or county park, or any land open to a wide variety of users, especially one where overnight camping is either forbidden or infrequent (for example, if it is located in a well-developed metropolitan area), one can expect much more casual users who are not used to finding trails and appreciate frequent blazes.
Single-track trails of the sort favored by those on foot also receive more blazes than those that follow old roads or other wide routes, which are often self-evident and are thus usually blazed only as necessary to infrequently reassure travelers of the route they have chosen.
On a large piece of land, there is likely to be at least more than one trail. While it might seem obvious that, at minimum, trails should at least take different colours, this is not always done. In Mount Greylock State Reservation, which contains the highest mountain in Massachusetts, all trails other than the Appalachian Trail use the same blue blaze.
Blaze type might also be mixed when different user groups (i.e., snowmobilers, horse riders, mountain bikers) are allowed on trails. For users of faster vehicles, blazes are often more outsized in order to be seen better at high speeds, and sometimes affixed markers best communicate who may and may not use a trail besides those on foot.
Another possible distinction is by season. In Norway, it is common to use blue for summer routes and red for winter routes. Red routes may traverse lakes and swamps, which are flat and well suited for cross-country skiing in winter, but impassable on foot in summer.
Colours are often assigned simply with an eye toward making sure that no two trails that intersect use the same one, but it can go further than that. On all state land in New York's Catskill Park, for instance, primary trails, especially longer "trunk trails" that go great distances, use red markers if they go in a generally east-west direction and blue if they go north-south. Shorter spur, loop or connector trails generally use yellow blazes.
On occasions when two trails run concurrently, usually at a slightly staggered junction, only one trail may be signed, often with the longer or more heavily trafficked trail's blaze predominating. In other cases, such as southern Vermont where the Appalachian Trail and the Long Trail follow the same path, both trails may use the same white blaze.
A quite different blazing system, called mute blazes was created in the Czech part of Krkonoše. The blazes, cut out of sheet metal, painted red, are suspended on high poles, thus visible for both hikers and skiers. Unlike in classic systems, they do not refer to paths or trails, but show the way to the nearest mountain huts and adjacent towns and villages with the possibility of overnighting and catering.
Meaning of blazes 
Even within the confines of a single trail, blazes may do more than simply reassure the trail user he or she is on the trail. They can alert the users to imminent turns, particularly if there is some confusion about what might be the trail, which can occur often in open woods, rocky open areas or on lightly used trails, switchbacks, and where trails begin and end.
Volunteers working in Harriman State Park in the 1930s for the newly-formed New York – New Jersey Trail Conference developed a system whereby a vertically stacked pair of blazes, with the upper one generally offset in the direction that the trail turns; a triangular pattern of blazes would indicate a terminus, its point up or down depending on whether that was the beginning or the end. These began to be used elsewhere and are now fairly common throughout North America, though variations of this system exist. Some trails instead use two blazes painted together at an angle to form an "L" shape to indicate a turn, with the angle between the two blazes indicating the angle and direction of the turn. Also, a few trails indicate turns with two stacked blazes, without an offset, but this can cause confusion as the direction is not implied. In addition, other trails may use two non-offset stacked blazes indicate the trail goes straight at a location where there may be tempting mis-turn.
A triangular pattern with its point to the side was also devised for eventualities like spurs or junctions, but these have not caught on.
In some areas, a triangular pattern with its point up indicates that a hiker is at the point of a sharp switchback.
As noted above, this system does much to encourage the use of paint blazes. Markers can also follow these patterns, but they less frequently use them. It cannot be used with cairns or tape flags, and not easily with carved blazes.
In the Netherlands, blazes usually consist of two bars above each other: white-red, yellow-red and red-blue are commonly seen blazes. An upcoming turn is indicated by duplicating the blazes: white-red-white-red, yellow-red-yellow-red, etc. Nowadays, stickers are used a lot, and instead of duplicating the blaze, the rectangle is cut into an arrow, to indicate direction. A saltire is used to indicate a direction should not be taken: the cross will have the same colours as the blazes (each bar will use a different colour).
A blaze on a tree in Slovenia (the so-called Knafelc blaze, named after Alojz Knafelc)
Tourist trail signs for cycling (top) and hiking (bottom) in the Czech Republic
An official NYSDEC marker in Catskill Park. Note protruding nail to allow for tree growth
Typical blaze on the Appalachian Trail
Mute sign in Krkonoše
See also 
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