Social capital is built via the network of connections among individuals in a community. Interactions among individuals within such a network make various endeavors more successful than they would be without such connections. The community becomes something more than a collection of individuals, because this structure has beneficial effects on economic and other efforts of community members, and provides benefits to the community as a whole. While benefits of social capital are well documented, the mechanisms of social capital -- how it produces such benefits -- are less well understood. Several mechanisms have been suggested, however, and these can form the basis for the structure of system dynamics models with which these various hypothesized mechanisms of social capital can be examined. One can more clearly define social capital by using the structure of these models.