Along the path next to the river I still see Yellowjackets scraping wood fibers off the fence with their sturdy mandibles. They will then chew these fibers and make a paper pulp in which to build their beautiful, study nests for the season.
The outer layer of the fence has turned gray and softened. The lighter parts are where Yellowjackets have removed a thin layer of fibers to expose the unweathered wood below.