Native Americans bent trees to create trail markers, but while thousands of the trees remain today, it can be difficult to find one.

When making a trail marker, a Native American would look for a sapling with a trunk about three-fourths of an inch in diameter. The sapling would be bent in the direction that should be followed and then secured in that position by one of several methods.

Sometimes the saplings would be tied down with rawhide, bark or vines, but other times the tiny trees would be weighted down by a rock or a pile of dirt. Once secured, the sapling would be left in this bent shape for a year to lock it in position, at which point, even after it was released, it would continue to grow pointing in the intended direction.

Source: Trail trees are a living Native American legacy | MNN – Mother Nature Network