unofficial paths or just their junctions with official trails. They may become obscured by snow in areas with heavy winters and may be easily knocked over. In some areas the recreational building of numerous cairns has obscured the proper use of cairns to mark junctions and crossings. In some areas of the United States, park rangers and land managers must disassemble excess cairns when they become eyesores or when they mislead navigation. Where rocks are scarce poles can be used. Poles are also frequently used to mark ski and snow shoe trails. Trail ducks Duck is a term used in some parts of the US, generally for a much smaller rock pile than a cairn, typically stacked just high enough to convince the observer it is not natural. For most, two rocks stacked could be a coincidence, but three rocks stacked is a duck. In some regions, ducks also contain a pointer rock (or a couple of stacked rocks) to indicate the direction of the trail. Crosses A wayside cross is a cross by a footpath, track or road, at an intersection, along the edge of a field or in a forest, which often serve as waymarks for walkers and pilgrims or designate dangerous places. They are particularly common in Europe, for example in Germany, Galicia and the Alps. It can be made of wood, stone or metal. Most wayside crosses are designed as crucifixes. Prominence In US wilderness areas, whether state or federal, the US Wilderness Act requires that the land seems "untrammeled by man," and so blazes are often kept to a minimum. By contrast, in a typical municipal, county, or state park, or any land open to a wide variety of users, or in a well-developed metropolitan area, blazes will be more frequent. Single-track hiking trails also receive more blazes than those that follow old roads or other more obvious routes. Systems On a large piece of land, there is likely to be 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