What is a wall to a child? It may be an obstacle course, a balance beam, a “car,” a seat, a home for spiders and ladybugs, a place to play hide and seek, a support to lean on when learning to walk, a perch for cats, a musical instrument to be played with sticks and hands. Rather than just a barrier, the wall can also become an incitement to explore that which lies beyond it. So how does a wall become just a territorial marker—a designation of private property, an imposing boundary line that cuts through space, dividing mine and yours? And what can children's engagement with the boundary, and the legalized attempts to prevent and punish their boundary-crossing, tell us about the social work of private property? In addressing these questions, we aim to take seriously the iterative “why?” of small children when confronted with territorial rules and related violence.