The premise of a primary key is simple enough: every record or row in a table should have some number or string that can uniquely identify it. Primary keys are essential for linking data spread across database tables, and for looking up and retrieving data from specific records. Yet for an identifier that seems so straightforward and uncontroversial, we find myriad ways that this unassuming bit of infrastructure has an outsized influence in human services work. Through case studies of the organizational networks of two nonprofit human services organizations, we find that different stakeholders use variants of identifiers to support work practices that are far more complex and social than the linking of tables or the lookup of data. Yet we also find that the low-level technical properties of the primary key are often coercive, forcing end-users to work on the infrastructure's terms-influencing the nature and order of the work, creating new forms of work, and influencing the tenor of the relationships among stakeholders. The technical abstractions of the underlying infrastructure, then, start to become the de facto public policy. We conclude by offering design provocations for better supporting identification across a variety of contexts.