HOUSTON Aug. 3 — Like pulling a receipt from an ATM, spacewalker Steve Robinson Wednesday extended his right arm and gently removed two strips of ceramic-fiber cloth from the heat shielding on the bottom of space shuttle Discovery, completing the first in-flight repair of a space shuttle with clockwork ease.

Robinson, perched on the end of the International Space Station’s 55-foot crane, began his ride over the side of Discovery at 8:22 a.m. EDT, then stopped about seven feet from the first strip, which was sticking out from the face of the heat shielding tiles that cloak the underside of the shuttle.

“I can see it very well,” Robinson said. “It looks to be close to three inches on one side and 1 inches tall. It looks to be bent over… . I’m ready to go in and get it when you are.”

Inside the space station, astronaut crane operator Jim Kelly maneuvered the controls to bring Robinson within arm’s reach of the “gap filler,” talked onto the target by a succession of careful commands: “Good motion … good motion,” Robinson intoned.

“Your hand is still the closest thing to the orbiter,” Kelly said, using Robinson’s extended arm as a reference point to avoid inadvertently bumping the tiles.

Seconds later Robinson gave the final command: “Three … two … one … stop. Brakes on.”

“Brakes on,” Kelly repeated.

A moment later, Robinson reached out with his stubby, spacesuited fingers and, without touching the bottom of the shuttle, matter-of-factly grabbed the gap filler and pulled.

“It’s coming out very easily,” he said. “Okay.”

In his hand he held a small triangular piece of gap filler about the size and shape of a very large guitar pick. It was stained with the red adhesive that had come loose, causing the filler to slip out during Discovery’s launch.

Ten minutes later Robinson held the second one — like a paint sample from a hardware store: “Probably even less force,” he said. Then he asked Kelly to move him five feet back from the orbiter so he could take some pictures of his handiwork.

Robinson and fellow spacewalker Soichi Noguchi had left the shuttle airlock at 4:48 a.m. to undertake a series of jobs that was expected to keep them scrambling over Discovery and the International Space Station for well over seven hours.

Around halfway through the spacewalk, the two astronauts and colleagues aiding them from inside began an elaborately choreographed series of steps to strap Robinson to the end of a crane and dangle him beneath Discovery.

Once there, he moved carefully along the surface of the shuttle’s heat shielding, giving commands to crane operators Kelly and Wendy Lawrence to reach the first of two “gap fillers,” strips of insulation protruding from between the orbiter’s thermal protection tiles.

If allowed to remain in place, the gap fillers could have triggered hot spots in the shielding during reentry, raising temperatures to unacceptable levels, NASA officials feared.

Analysts were unsure whether the fillers posed a hazard, but decided to remove them as a precaution.

Robinson’s historic repair was somewhat delayed early in the spacewalk while he and Noguchi, aided by a crane, wrestled a three-ton stowage platform out of the shuttle and into position on the space station.

Balky fasteners delayed completion of the job — the only part of Discovery’s mission linked directly to the shuttle program’s stated purpose of finishing assembly of the station by 2010.

Installation of the platform was planned long before the Columbia tragedy grounded the shuttle fleet for 2 years, and was to be a centerpiece of Discovery’s flight, but the task was overshadowed by the attention focused on Robinson’s trip to the shuttle’s underbelly.