Astronauts have attached arms to the space station's new robot, Dextre.
Dextre will remove the need for some spacewalks in future
Richard Linnehan and Michael Foreman completed the task during a gruelling spacewalk outside the orbiting platform that lasted more than seven hours.
The robot, which is properly called the Special Purpose Dextrous Manipulator, will in future do much of the external work on the space station.
The 1.5-tonne, 4m-long machine was brought up to the platform by shuttle Endeavour on Tuesday.
It was packed in parts on a travel pallet and needs to be reassembled before it can begin work.
During the mission's first spacewalk on Friday, Dextre's hands were fitted to its arms. Now those arms have been attached to the robot's torso.
Dextre will be used to install and remove small payloads such as electronics boxes, computers and batteries.
It will be controlled by astronauts from inside the platform or even by ground controllers.
Endeavour's astronauts and the resident crew on the space station have continued to outfit the new Japanese Logistics Module which was also lofted on Tuesday.
This is a storage facility for the Japan Aerospace Exploration Agency's (Jaxa) Kibo laboratory, the main section of which will travel to the station on the next shuttle flight.