If the International Space Station were a city, then the truss that connects its modules would be, among other things, its power plant, public transportation, and closed-circuit surveillance systems.

Working near and within the complex’s backbone truss, the two astronauts ... in total supporting the assembly, maintenance and upgrade of the International Space Station since 1998.

Thursday’s spacewalk was the 274th EVA in support of assembly, maintenance and upgrade of the International Space Station ...