So whilst doing PFLs - you must remain more than 500ft away from any person, vessel, vehicle or structure.
You are unlikely to (and should not) get that close to a person, vessel or vehicle while conducting a PFL-the only real problem is a fence or hedge-so a lawyer would have to argue whether a fence or hedge is a structure--in my opinion a hedge is definitely not a structutre and neither would I think a fence is--i think that the law is written to describe a structure as something that would house a vehicle, vessel or person.