Resources often produce more value in combination than they do separately: think of segments of a highway or parts of a machine. I argue that property’s defining purpose is to group together complements, and that property law and theory should focus on identifying and realizing valuable bundles of resources. While some complementarities align with traditional asset boundaries and can be protected by exclusion rights, realizing others requires crossing or eschewing boundaries to recombine resources in ways that further larger social, economic, or ecological objectives. The gains associated with the entrenching and excluding functions of property thus vie with the gains that come from breaking through those entrenchments to reconfigure resour...