Astronauts gave the International Space Station's big robot arm a new hand in what was the first of three Nasa spacewalks planned over the next two weeks.
Commander Randy Bresnik and Mark Vande Hei floated out on a space walk on Thursday morning.
The latching mechanism on one end of the 58-foot robot arm malfunctioned in August.
The arm has to be replaced before an Orbital ATK supply ship launches in November.
This bundle of latches, more than three feet long, is used to grab visiting spacecraft.
It also attaches to grapple fixtures outside the space station.
The Canadian-built arm has been in orbit for 16 years and engineers attribute the recent trouble to wear and tear.