How can an organization help participants increase their social capital? Using data from an ethnographic study of Launch, an organization that prepares low-income students of color to attend elite boarding schools, I analyze how the organization's structures not only generate social ties among students but also stratify those ties horizontally and vertically, thereby connecting students to a set of social contacts who occupy a range of hierarchical positions and who are able to provide access to resources that are beneficial in different contexts and at different times. I argue that organizational structures can function as tools for building--and embedding participants within--social networks with advantageous structural characteristics.