American Steve Marino, who had to use his father as a passport courier to take up his place in The Open Championship, set the clubhouse target at Turnberry.
Marino began the day three off the lead held by Spain's Miguel Angel Jiménez, the 45 year old having equalled the lowest first round in Open history with his 64.
But as Jiménez and many others failed to cope with a strong wind on the Ayrshire links, Open debutant Marino carded a second round of 68 for a five under par halfway total of 135.
Marino was originally third reserve for the championship and only received a call-up on Sunday, by which time he had dispatched his father from Virginia to Florida to collect his passport and post it to Illinois, where he was playing in the John Deere Classic.
"I replaced Shingo Katayama and I found out Sunday morning," explained Marino, who holed out from 116 yards for birdie on the third, holed a bunker shot on the sixth for another and eagled the 17th.
"I was at the John Deere. I didn't have any warm clothes. I didn't have a passport. I had to fly my dad to my house in Florida so he could get my passport and FedEx it to me at the John Deere. He left Friday morning and flew back Friday night!
"I wasn't even expecting to play in this tournament. I didn't think I was going to be an alternate, let alone be playing. So when I found out I got in, I was super-excited.”
Marino admitted this week was his first experience of links golf, the 29 year old from Oklahoma adding: "I'm just really looking forward to playing golf here the next few days.
"I've really enjoyed myself here, I love the golf course. I love the challenge that it presents. You have to drive it straight, and most importantly, you have to stay patient and stay positive out there, because once you start getting down on yourself and thinking negatively, it will go bad real quick.
"I've played four links rounds ever, two practise rounds and then the first two rounds. They have links courses in the States, but I wouldn't really call them links; it's not like it is over here. But it's awesome, I'm really just enjoying it and having fun. I'm just having a blast."
Marino was one shot ahead of 1989 Open Championship winner Mark Calcavecchia, who added a 69 to his opening 67 to finish four under par.
Overnight leader Jiménez was another shot back on three under after an inward nine of 34 helped him salvage a round of 73, while England's Ross Fisher, South African Retief Goosen and Japan’s Kenichi Kuboya were also on the same mark.
Fisher, who is ready to pull out of the event at any minute if his wife Jo goes into labour, birdied three of the last four holes for a 68, while former US Open Championship winner Goosen recorded a 70.
Tiger Woods was facing an uphill battle to make the cut.
After an opening 71, Woods birdied the par five seventh to get back to level par, but promptly bogeyed the next two holes to drop back to two over at the turn.
And the World Number One then lost a ball after a wild tee shot on the tenth to run up a double bogey six, leaving him one shot outside the projected cut mark and in danger of missing only his second cut in 49 Majors as a professional.
The only other missed cut came in the 2006 US Open Championship at Winged Foot just weeks after the death of his father, Earl.
