I have several friends that "claim" sites like this all the time. Thee have a small pup tent and two cheap chairs that they leave at the site. One guy even has solar powered small latern that comes on when it's dark that he leaves by the side of the tent. The only time he does this is when it is a free site. If he can pay for the site several days in advance, it's his and I have to agree with that tactic. He gets the site he wants for the weekend and the park gets revenue that they normally would not have gotten because of their no-reservation policy. This is especially rampant in Oklahoma state parks.