Astronauts Patrick Forrester (left) and Steven Swanson participate in the STS-117 mission's fourth and final spacewalk. Among other tasks, Forrester and Swanson continued activation of the station's new starboard 3 and 4 (S3/S4) truss segments; checked out the Drive Lock Assembly 2, one of two mechanisms that will drive rotation of the S3/S4 Truss Solar Alpha Rotary Joint (SARJ); and, removed the final launch restraints on the SARJ.