MoapaPk wrote:In the west, rocks falling down slope and hitting trees make marks that look like blazes; hence it is necessary to make the blaze double to make it look unnatural (and humanly produced).
This one doesn't make much sense to me. Rocks falling downhill will damage the trees at the edge of the forest near a cliff or very steep slope. But it must be a very rare rock that can bounce up to five feet in the middle of a forest and make a blaze. Bears or falling trees seem far more likely culprits. I agree that the blaze should be recognizable as human-made to be most useful.
I did some searching and found the following. Seems perhaps this is just USFS standard blaze.
"Although blazing systems vary, in the United States many systems follow the U.S. Forest Service standard. These blazes are carved into the bark of trees on the right side of the trail, about 5 feet (1.5 meters) up from the ground. They consist of a rectangle that's 4 inches (10 centimeters) wide by 8 inches (20 centimeters) long, with a 2 by 4-inch (5 by 10-centimeter) smaller rectangle carved above it. It looks like a lower-case letter i." source