Fixed I suppose. I started out with two fiberglass reflector poles. Those worked well enough but I had to hammer them back into the ground after removing them to mow and one of them got run over. After I broke the top off the second one with a little too much mallet persuasion I upgraded. These poles have a spike that stays in the ground and a spring on the bottom so the should survive a brush with a bumper better. Not really ideal but cheaper than adding more asphalt.
Lawn by
willtel, on Flickr