S118-E-09144 (18 Aug. 2007) --- Astronauts Clay Anderson, Expedition 15 flight engineer, and Dave Williams (out of frame), STS-118 mission specialist representing the Canadian Space Agency, participate in the mission's fourth and final session of extravehicular activity (EVA) as construction and maintenance continue on the International Space Station. During the 5-hour spacewalk, Anderson and Williams installed the External Wireless Instrumentation System antenna, attached a stand for the shuttle's robotic arm extension boom and retrieved the two Materials International Space Station Experiments (MISSE) to be brought back on the shuttle.