Refers to a movable pole with a flag set in the center of a hole. The flag is marked with a number of holes which indicates the position for players to leave the putting green.
Flagpoles have been used for many years, but it has no definition in the rules of golf before 1952.There was only one sentence in rules of 1952: the flagpole was a movable pole placed in the center of putting green hole with or without a flag in order to indicate the positions. Golf encyclopedia
In 1960, the rules committee found that if the flagpole was not round, there would be many problems. The golfers were benefited from rotating the flagpole. So when the rules were revised in 1960, there was an added line about the flagpole: the cross section of flagpoles must be round. Golf encyclopedia
In 2004, it was discovered that flagpoles made of soft material can absorb the impact and keep the ball from bouncing off. Therefore, a final sentence was added to the rule: the use of materials that can absorb the impact force and influence the movement of the ball is prohibited.
Since the rules did not mention the height of flagpoles, the USGA recommends that the height should be no less than 7 feet. In Scotland, you'll find that the flagpoles are much lower than this, in order to prevent the wind from blowing it away.
The USGA also recommended the diameter of a flagpole should be 3/4 inches, which could leave enough space around, and even if the flagpole is not removed, the ball can roll into the hole. Golfers who make a hole in one shot should appreciate the suggestion."