American pair Justin Thomas and Ryan Moore both fired on the back nine to take a joint lead at the halfway stage of the SBS Tournament of Champions in Hawaii.
Thomas struck four birdies in his final eight holes while Moore sank in five in seven to sit at top of the leaderboard on 12 under, two shots clear.
Thomas, who went round in a six-under-par 67, might have been a solo leader had he not bogeyed the par-five 15th, his only blemish of an otherwise fine round.
Moore also had one bogey, on the par-three second, and also carded a 67, leaving his best for the back nine.
First-round leader Jimmy Walker and Patrick Reed are on 11 under, Reed recording the best round of the day with a superb eight-under 65.
World number one Jason Day is four shots further back on seven under and will have to improve if he is going to make an assault on the first title of 2017 while number three ranked Dustin Johnson is also on seven under going into the weekend.