SANTA CLARA – Only three teams have more penalties this season than the 49ers, who have 21 in just the last two games.

Of particular concern to coach Jim Harbaugh and offensive coordinator Greg Roman are the eight offensive holding penalties in the last two games that have halted drives and put quarterback Colin Kaepernick in third-and-long situations.

"That's something we've got to get a lasso around real quick," Roman said Thursday. "49ers football (is) smart, tough, opportunistic football. And penalties certainly don't fit into that equation."

The two players with the most penalties are guard Mike Iupati and special-teams player C.J. Spillman. Both have been flagged seven times, although one of Spillman's was offset.

Safety Dashon Goldson leads the team in yards penalized. He's been flagged six times for 87 yards. Goldson is ninth in the NFL in penalty yardage; cornerback Chris Culliver is 25th.

Also noteworthy are the players who haven't committed a lot of penalties.

Only one 49ers wide receiver, Kyle Williams, has been flagged this year. Tight end Vernon Davis, who has played virtually every snap and who was notorious for false starts early in his career, also has not been penalized. First-time starter Alex Boone, who never played guard before this season, has been called for only one penalty.

Steel beaming – Most of the steel on the 49ers' new stadium is in place, and the team celebrated the milestone with a "topping out" ceremony in which two steel beams were placed at the highest point in the stadium.

Jack Hill, the project executive for the stadium, said the venue is 28 percent complete and the steel section is 90 percent finished. Soon the workers who have been part of that phase will be replaced by workers who specialize in other areas.

"We're reaching the point where we're kind of seeing the end of one phase," Hill said. "We thought it would be a good time to celebrate that."

The two steel beams were painted gold and signed by members of the 49ers – including coaches and players – as well as the construction workers.

The stadium is scheduled to open in 2014.

Injuries – Cornerback Tarell Brown (hamstring) returned to practice on a limited basis, but receiver Mario Manningham (shoulder) missed his second day.

If Manningham is unable to play Sunday, first-round pick A.J. Jenkins could see his first action of the season.

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