Boundaries in Hypernetwork Theory (HT) are non-structural tags that restrict visibility without altering the underlying hypernetwork. They attach to hypersimplices as annotations and participate in no identity, typing, or alpha/beta semantics. Projection over a boundary, B(H, b) = pi_b(H), is filtering only: it selects exactly those hypersimplices carrying b and preserves all axioms of the structural kernel. The backcloth remains immutable, and no new structure is created, removed, or inferred. This paper formalises boundaries as a simple and conservative scoping mechanism. It clarifies their syntax, their interaction with projection, and their use in producing identity-preserving subsystem views that support modular modelling and overlapping perspectives. The account also makes explicit why conservative scoping matters: boundaries provide reproducible view extraction, stable subsystem isolation, and safe model exploration without altering the global structure. Scoped operator application is defined as ordinary structural-kernel composition applied to projected views, ensuring that view-level reasoning remains local and does not modify the global hypernetwork. This establishes a disciplined separation between immutable structure and scoped analysis while retaining full compatibility with the structural kernel. The paper includes a worked example demonstrating how boundaries yield coherent, identity-preserving subsystem views and how scoped reasoning supports refinement within these views. The result is a precise and minimal account of boundaries that complements - but does not extend - the structural kernel and completes the scoping mechanism required for practical multilevel modelling with HT.