Many people travel in vans, class b's or class c motorhomes that do not have a toad. If they have paid for a site, as hosts we instruct them to leave chairs or something on the site to show it has been taken. If someone came into the campground and "moved" that persons personal possessions off the site and moved in, we would make them move. If you have a concern about whether a site is taken or not, please go talk to the host. In most campgrounds, even first come first serve, self pay - you will usually get a stub to put on the site post also to show it is taken.