Spacewalkers Dave Williams (L) of the Canadian Space Agency and Rick Mastracchio (R) secure a cover over the newly installed Control Moment Gyroscope on the exterior of the International Space Station in this view from NASA TV August 13, 2007.

Spacewalkers Dave Williams (L) of the Canadian Space Agency and Rick Mastracchio (R) exit the airlock for their extravehicular excursion in this view from NASA TV August 13, 2007.