I called the rangers today. I had a couple questions about camping at a Campground. I got around to asking about hammocks. The ranger told me as long as I did not put nails in the trees it was fine. He went on to say that it was ok to screw eyebolts into the trees as long as I remove them before I left. He said it wouldn't hurt the tree it would heal in no time. What are they thinking? Sure one time will heal fine but get dozens doing it and well you get my point.