In a library you protect your space with a book, coat, or note-book. You 'save a place' in the theatre or at the beach reserving a spot that is 'mine' or 'ours'. Juvenile gangs fight to protect their turf. Neighbours of similar ethnic backgrounds join forces to keep other groups out. Nations war over contested territory.
Pastors accuse others of 'sheep-stealing'.
Help me to figure out the good and bad aspects of this universal habit of humans. I placed the sand as a boundary for the sea, a perpetual barrier that it cannot pass. There's good news and bad news here. Individuals and families ought to have boundaries - physical, material, emotional and others ought to respect those boundaries. Indeed, boundaries define us, in many ways.