Spacewalker Paul Richards at work outside the International Space Station on Tuesday. Photo: Spaceflight Now/NASA TV

Sometimes, the best way to free a stuck piece of hardware is to give it a good whack.

That's what spacewalker Andrew Thomas did this morning to free a jammed, spring-loaded locking pin at the base of a strut holding one of the international space station's two huge solar wings in place.

Three of four such pins in the so-called "four-bar linkage" supporting the port-side solar wing engaged properly when the wing was deployed in December. But the fourth refused to lock.

Early today, working nine stories above the shuttle Discovery's cargo bay, Thomas tapped the brace with a hand tool and to the delight of flight controllers, the pin suddenly snapped into position.

"Yep, that tap worked," fellow spacewalker Paul Richards observed.

"That's it," Thomas agreed. "It's in, isn't it?"

A spacewalker appears in silhouette against one of the giant space station solar arrays. Photo: Spaceflight Now/NASA TV

"It looks like it. Let me look at it from this side."

"The pin is in. I got it," Thomas said.

"You got it, Andy. Great job!"

It was a fitting conclusion to a very deliberate, carefully conducted spacewalk, the 102nd such excursion in U.S. space history, the 62nd in the history of the shuttle program and the 18th devoted to space station assembly.

During a marathon spacewalk overnight Saturday by station astronauts James Voss and Susan Helms, a critical robot arm attachment fitting was lost in space when it somehow slipped away from Voss.

Thomas and Richards, both spacewalk rookies, took elaborate care today to keep up with all their tools and hardware and in the end logged a near perfect six-hour and 21-minute excursion.

Spacewalk planner Kieth Johnson said lead flight director told him to "accentuate the positive" in today's post-spacewalk news briefing.

The spacewalkers prepare electrical connections for the arrival of the station's robot arm on the next shuttle mission. Photo: Spaceflight Now/NASA TV

"I said, well that's easy. There were no negatives," Johnson said. "This was a very successful EVA."

Eighteen U.S. and Russian astronauts have now logged 124 hours of spacewalk time building and equipping the international space station.

"Wow!" Richards marveled as he floated into the shuttle's cargo bay. "My first sight is a very beautiful sunrise."

"Speaking of which, make sure your visors are down," Helms reminded.

Taking a strictly business approach, the spacewalkers seldom commented on anything other than the work at hand. But Thomas, a native of Adelaide, Australia, took a brief moment to enjoy a view of his hometown as it raced by 236 miles below.

Thomas works to install a cargo platform to the Destiny module. Photo: Spaceflight Now/NASA TV

"It's an amazing view up here," he said. "I'm passing over south Australia and I can see the coastline, my hometown, all very clearly. Quite extraordinary."

After attaching a cargo storage platform to the Destiny module's hull, the astronauts attached a spare cooling system pump and hooked up cables that will route data and video into the lab from the station's robot arm.

The Canadian-built arm is scheduled for attachment during a shuttle flight next month.

"Nice work, guys," Helms radioed when the work was complete. "You guys are just doing great. This has been fabulous."

The spacewalkers then made their way to the top of the P6 solar array truss to tap on the jammed four-bar linkage.

Thomas opens a panel on the side of the Destiny laboratory module. Photo: Spaceflight Now/NASA TV

While at the top of the P6 solar array, the spacewalkers also inspected status lights on a device designed to measure the electrical environment around the space station.

The Floating Potential Probe, or FPP, has worked intermittently since installation late last year. It was working late last month when the space station's crew briefly left the outpost to move their Soyuz lifeboat to a different docking port.

When they re-entered the station and powered up its computers, the FPP refused to operate.

Thomas and Richards inspected the device first hand today, looking for signs of life from three LEDs on a front panel. Blinking LEDs would have indicated normal operation.

"I see three LEDs, no lights. See 'em?" Richards asked his crewmate.

"OK, understand no light," astronaut Susan Helms called from Discovery's flight deck.

. "No lights," Thomas confirmed.

"Well then I guess they're not blinking," Helms said. "Thank you very much."

Thomas works to unbolt a spare cooling pump from a craddle in Discovery's cargo bay. Photo: Spaceflight Now/NASA TV

The FPP was mounted on the station last year to measure the effectiveness of two other devices, called plasma contactors, that release xenon atoms into space to electrically ground the station.

The concern was that potentially dangers charges could build up, posing a risk to spacewalkers.

Earlier data from the FPP showed the risk was minimal with both plasma contactors operating and the station's main solar arrays oriented edge on to the direction of travel.

Engineers would like to operate the arrays normally during spacewalks, allowing them to track the sun, but more data is needed to fully understand the electrical environment. It is not yet known what might be needed to restore the FPP to operation.

"And Houston, Discovery, I suppose you heard, but we had a successful task for the four-bar linkage pin," Helms reported.

"Yes, we copy that Susan, that is absolutely outstanding work," astronaut Shannon Lucid replied from mission control.

"And none of the FPP status lights are on, Shannon."

"OK, we copy, no status lights on the FPP."

Thomas climbs back aboard Discovery after a successful spacewalk. Photo: Spaceflight Now/NASA TV

A few moments later, Thomas and Richards began making their way back down the P6 truss toward Discovery's airlock.

"Well Andy, we were on top of the world there," Richards said.

"We were for a while, yeah," said Thomas.

The excursion began at 12:23 a.m. and officially ended at 6:44 a.m. when the astronauts began repressurizing Discovery's airlock.

"You all did an outstanding job," Lucid radioed.

"Thanks a lot," Richards replied. "It takes a team effort and we had a lot of good people on the team."

The repressurization process was interrupted briefly and the airlock taken back to vacuum to complete an engineering test in which the shuttle's primary jets were fired to determine their effect on the combined shuttle-station "stack."

Even though the airlock was depressurized, the official end of the spacewalk was recorded as 6:44 a.m.