|RBC Heritage second-round leaderboard|
|-6 K Chappell (US), C Hoffman, (US), J Day (Aus); -5 L Donald (Eng), R Knox (Sco), P Kizzire (US)|
|Selected others: +1 G Owen (Eng); +2 I Poulter (Eng); +3 P Casey (Eng), M Fitzpatrick (Eng); +5 G McDowell (NI)|
Luke Donald and Russell Knox are one shot off the lead at the RBC Heritage at Hilton Head in South Carolina.
Former world number one Donald, 38, shared the lead after the opening round but a level-par round of 71 for the Englishman on Friday saw him reach halfway on five under at Hilton Head.
Scotland's Knox, 30, shot a six-under 65 to join Donald in tied fourth.
World number one Jason Day and Americans Kevin Chappell and Charley Hoffman share the lead on six under.
Knox, who won his first PGA tournament at the WGC-HSBC Champions event in November, shot eight birdies in his 66, the best round of the day.
Donald is without a PGA or European Tour win since 2012, but was on two under for his round heading into the back nine before double bogeying the par-three 14th.
American Patton Kizzire sunk a 41-foot putt to make birdie on the 18th and join Knox and Donald on five under par.
England's Greg Owen and Ian Poulter made the cut, but Paul Casey and Matthew Fitzpatrick missed out on three over par.
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