Davis Love III opened up a two-shot lead at the halfway point of the Open by shooting a second-round 72 to leave him at one under par.
Denmark's Thomas Bjorn and Korean SK Ho are tied in second place at one over, while Alastair Forsyth leads the British challenge on two over alongside Sergio Garcia and first-round leader Hennie Otto.
Tiger Woods appeared to be heading for the lead before a four-putt on the 12th left him just off the pace at three over.
And reigning champion Ernie Els put himself back in contention a shot further back with a 68, the round of the day.
"I'm putting real well, and I've had two or three putts that maybe I did not like over two days," said Love.
He led by three strokes at one stage, thanks to birdies at the seventh, ninth and 11th but bogeys at the 10th, 12th and 13th sent him dropping back and problems at the 17th set him back further.
But he was fortunate when his ball struck an out-of-bounds marker at the par-five 14th and bounced back into play.
-1 D Love (USA)
+1 SK Ho (Kor), T Bjorn (Den)
+2 A Forsyth (Sco), B Curtis (USA), Hennie Otto (SA),
T Levet (Fra), S Garcia (Spa),
K Perry (USA), M Ruiz (Par)
"That was three good bounces all used up in one shot," he said.
He looked like making another bogey at the last after driving into the rough but managed to save his par for a round of 72 to follow on his opening round of 69.
"This course is a great test. It lets you get a few early birdies and then it just gets harder and harder," he added.
Bjorn had birdies at the fifth and seventh with his only bogey in between.
SK Ho, playing in his first Open, was one of only five players to break par on Thursday and when he birdied the third and eagled the fourth on Friday, he suddenly had a two-shot lead over the field.
Three bogeys in four holes around the turn saw him drop back off the pace, but a 73 and one-over total of 143 had the 29-year-old from Seoul just two off the lead alongside Bjorn.
Marco Ruiz of Paraguay, who had to qualify for the Open, could have joined Ho and Bjorn on one over but for a bogey at the last.
The cut came at eight over and 75 players will be back for the weekend.
Among those who missed the cut were Jose Maria Olazabal, Lee Westwood, Bernhard Langer, US Open champion Jim Furyk, English youngsters Justin Rose, Paul Casey and Luke Donald, and former winners Paul Lawrie, Justin Leonard, David Duval and Sandy Lyle.
Nick Faldo made it with nothing to spare on his 46th birthday, grabbing a
birdie at the difficult 17th.
Phillip Price led the Welsh challenge on four over, with Ian Woosnam slipping back to six over, while Andrew Oldcorn was the only Scot apart from Forsyth to be staying for the weekend.
Gary Murphy was the leading Irishman, but Paul McGinley, Darren Clarke and Padraig Harrington all made the cut.
There will be no amateurs in the final 36 holes, British champion Gary Wolstenholme, American title-holder Ricky Barnes and Cornwall's Scott Godfrey all bowing out.