The flag is named for its shape. It is a flag shaped like a knife, also known as an outdoor rotary screen or a feather flag, or a fan-shaped flag. It is a display prop for outdoor exhibitions. The modern street lamp advertising flag has no knife shape, most of which are square. The flag pole of the banner and the flex banner of the knife like flags can be stretched and easy to watch regardless of the wind. In the sand, the grass is inserted into the ground with a drill, and the cement ground has a cross base, a water bag or a sandbag.