Australia&aposs Jason Day climbed to the top of the leaderboard on six under to take the overall lead at the halfway mark of the Masters. Day, who tied for second at Augusta in 2011, rolled in six birdies and two bogeys to shoot a round-best 68 and move one stroke clear of a congested chasing pack. With blustery conditions and tricky pin positions making scoring difficult, Day carded a bogey on the fourth hole before rallying with four birdies in between holes five and 11. Another blemish at 12 had seemingly halted his momentum but the 25-year-old regrouped to pick up a shot at the very next hole before a birdie on 16 earned him the overall lead. He then saved par after finding the fairway bunker on 18 to hold onto a slender advantage heading into the third round at the year&aposs first major. Day leads from veteran Fred Couples and compatriot Marc Leishman, who sit a shot back on five under. American Couples, the 1992 Masters winner, fought back from two bogeys and a double bogey inside his opening seven holes to post a one-under 71 on Friday, while overnight leader Leishman hit three bogeys and two birdies in his 73. Angel Cabrera, the 2009 Masters champion from Argentina, shares fourth place with American duo Jim Furyk and FedEx Cup winner Brandt Snedeker. World number one Tiger Woods is a shot further back in a tie for seventh, the American dropping two shots late on in his round of 71. Woods is joined on three under by compatriot Jason Dufner, English trio Justin Rose, Lee Westwood and David Lynn, South Korean KJ Choi and Australia&aposs Adam Scott. A pair of former winners in Charl Schwartzel and Bernhard Langer remain in contention on two under overall, where they are joined by world number two Rory McIlroy of Northern Ireland, Australia&aposs John Senden and Spanish duo Sergio Garcia and Gonzalo Fdez-Castano. The second round was also marked with controversy, with rules officials handing 14-year-old amateur Guan Tianlang, the youngest player in Masters history, a one shot penalty for slow play. The teenage sensation nevertheless made the cut and enters the weekend on four over.