Sussex 181 and 277 for 3 (Orr 119, Haines 94) lead Kent 165 (Podmore 37, Atkins 5-51) by 293 runs
Ali Orr's maiden first-class century gave Sussex a commanding, but not conclusive, lead on day three of their LV= Insurance County Championship match with Kent at Canterbury.
Orr hit 119, including 19 fours, as Sussex advanced to 277 for 3, but they were stifled for long periods by the hosts, who trail by 293 going into the final day.
Orr's opening partner, Tom Haines, was out for 94 just before stumps to Matt Quinn, who took 2 for 88.
Earlier Jamie Atkins took career-best figures of 5 for 51 as Kent were dismissed for 165, Hamid Qadri finishing on 30 not out, his highest first-class score.
Kent began day three on 122 for 7 and lost Bailey Wightman in the first over when he was bowled by Atkins, but Quinn hung around for 38 minutes, providing useful support to Qadri, before he was caught behind off Ollie Robinson for 11.
By the time Jas Singh was lbw to Sean Hunt for two, Sussex's lead had been chopped to just 16, but Orr and Haines steered the visitors to 53 for nought at lunch and batted through the afternoon session. Kent never really looked like taking a wicket, but they were tight and disciplined, slowing the run rate to under three and limiting Sussex to 147 for no wicket at tea.
Orr reached three figures when he glanced Harry Podmore to third man for four and was finally out when he cut Singh to backward point and was caught by Dan Lincoln, having faced 254 balls over nearly five hours.
Harrison Ward made six when he drove Quinn to Heino Kuhn, who took a two-handed catch at point and the scoring rate slowed to 2.8 during the evening session, only nudging back over three when Travis Head hit sixes from successive balls in the 90th over, followed by two fours. Quinn then had Haines lbw in the third last over of the day, ending a painstaking innings of 233 balls and 354 minutes.
Head and Oliver Carter were unbeaten on 29 and 15 respectively at stumps, but Sussex face a potentially awkward decision over the timing of any declaration on day four.