Franklin Chang-Diaz and Philippe Perrin, visiting from space shuttle Endeavour, connected eight power, data and video cables. Then, working 240 miles above Earth, they drove four bolts to secure the platform and installed a TV camera.
Earlier this spring, 44 feet of track and a rail car were installed on the international space station for use in the later stages of construction. Tuesday's work involved the bolting of a $254 million platform on the rail car.
The platform will enable the robot arm and pieces of the space station to ride from one end of the space station to the other. A series of tests must be conducted over the next few weeks before the robot arm is commanded to climb onto the platform for a ride.
Eventually, the rail car will run the entire 356-foot length of a framework that is being installed at the space station.
The one-and-a-half ton aluminum platform was delivered by the shuttle last week.
At the end of the five-hour spacewalk, Perrin praised the Canadians for their platform. Canada also built the robot arm.
"They have put together a wonderful piece of hardware, and everything worked fantastic," the French astronaut said, repeating everything in French.
Tuesday's spacewalk was the second of three planned during Endeavour's visit. Chang-Diaz and Perrin will go out one last time on Thursday to tackle their most challenging job: robot-arm wrist surgery.
One of the wrist joints in the robot arm seized up in March and is being replaced.
Endeavour is scheduled to return to Earth on Monday after a 12-day mission.