Colt Knost has a two-shot lead after day two of the RBC Heritage in South Carolina.
The American hit five birdies at the Harbour Town Golf Links as his round of 67 left him on nine-under-par.
Sweden's Carl Pettersson is on seven-under, while American Boo Weekley is one of five players on six-under.
England's Luke Donald, who needs to finish inside the top eight to hold on to his world number one ranking, only just made the cut on two-over.
