This chapter focuses on retrofit to protect human beings from their environment: specifically, seismic retrofit of bridges to prevent them from collapsing in earthquakes. It also examines the characteristics of infrastructure that play into this global-local tension, the processes by which changes in sociotechnical systems become mobilized as worrisome problems, and the resulting practices of infrastructure repair, of which retrofit is one variety. The chapter is primarily about retrofit of infrastructure technologies, in particular those that are locally massive and difficult to change, such as buildings, roads, and bridges. To better explain how retrofit programs interact with global networks, the first Caltrans case study below covers changes in general engineering practice at Caltrans, and its relationship to broader political and professional networks. The second Caltrans case study focuses on the sociotechnical network surrounding one particular project, the seismic retrofit of the Coronado Bridge in San Diego, which illustrates the complexities that can attend local implementation of a systemic retrofit program.