Surrey 299 for 7 (Roy 120, Onions 4-68) trail Durham 401 (Jennings 201*, Footitt 5-90) by 102 runs
A plucky century by Jason Roy helped Surrey to 299 for 7 in reply to Durham's 401 in the Specsavers County Championship match at Chester-le-Street.
In spending 103 balls over his first 50, the England one-day batsman either missed it or middled it. But his second 50 required only 41 balls, with most of his last 20 runs being easy pickings off future team-mate Scott Borthwick.
He sat back to clobber a short ball from the legspinner between mid-off and extra cover to reach three figures with his 14th four.
But after sharing a third-wicket stand of 164 with Zafar Ansari four wickets went down for 24 runs.
Ben Foakes was lbw when he walked across, looking to turn Wood to leg, and Roy went for 120 when Onions skidded one through to knock him off his feet and claim another lbw verdict.
Onions produced another beauty four overs later to claim his fourth wicket, beating Tom Curran's forward push to trim his off bail.
Durham were twice convinced they had Roy caught behind, but his edges tended to be of the thicker variety, one flying wide of gully when looking to turn the impressive Brydon Carse to leg.
He hit Paul Collingwood's first ball just out of short extra cover's reach, and on 42 Onions had him in all kinds of trouble.
A ball which Roy played into the ground lobbed up and dropped just over the stumps, then he was beaten twice in the same over.
Onions also took two wickets in four balls shortly after lunch. He beat Dominic Sibley's forward push on 31 to nick the off stump then nipped one back to have Kumar Sangakkara lbw for 48. In the morning Jennings was left stranded on 201, becoming the seventh player to carry his bat through a Durham innings.
Although the fifth batting point was achieved when last man Onions scored the day's first seven runs, he then drove a catch to cover to give Mark Footitt his fifth wicket.
The only Surrey batsman to fall before lunch was Rory Burns, who was given an uncomfortable time by Wood and fell for 15 when an in-swinger took the inside edge on the way to wicketkeeper Stuart Poynter.
Faced with an attack of Wood, Onions, Ben Stokes and the pacy Carse, Sibley played well enough to suggest he won't be the one making way for Mark Stoneman, or Borthwick.
Carse, back after a three-month injury absence, posed the greatest threat. He beat Sangakkara twice in his first two overs and remained out of luck as he and Stokes emerged wicketless.