Cape Canaveral, Fla. ? Two spacewalking astronauts bolted a 44-foot girder to the international space station Thursday, completing the first step in one of the most complicated construction jobs yet at the orbiting outpost.

The 27,000-pound beam was first hoisted into place and clamped down by the space station’s 58-foot robot arm, operated by remote control from inside the spacecraft by two astronauts.

Then two other astronauts, Steven Smith and Rex Walheim, floated outside, unfolded two V-shaped struts on the girder and bolted them down. As he put the final twist on the last of eight bolts, Walheim shouted, “Hot dog!”

“We’re going to put in for your ironworker’s card,” NASA’s most experienced spacewalker, Jerry Ross, said from inside Atlantis.

Space shuttle Atlantis’ visiting astronauts will go out three more times to finish installing the $600 million girder, the first section of a framework that eventually will stretch 356 feet and hold a collection of solar wings, radiators and science experiments.

During Thursday’s outing, Smith and Walheim also hooked up power cables and fluid lines. Some of the hoses were stiff and twisted, and the tray containing them was hard to release. It took both of them to yank the tray loose.

That put the spacewalkers behind, so much so that Mission Control ordered Smith to briefly retreat to the station air lock Thursday afternoon and recharge his oxygen supply.

The spacewalk ended up lasting almost eight hours, more than an hour longer than planned. “You guys did a fantastic job today,” Mission Control said. “You’re probably ready to come on in.”