The Beavers lead the Rocks by three points with a four-goal advantage when they host Enfield Town with Bognor at home to Hendon on the final day.
Jason Prior gave the Rocks a 12th minute lead against an already-relegated Brentwood Town side in front of a crowd of 407 at Nyewood Lane. Two minutes after the break Connor Tighe added a second and right on time, Snorre Nilsen added the Rocks` third. Ryan O`Rawe scored a late consolation for the visitors.
Kingstonian will finish seventh - a fact confirmed by a 3-2 loss to Farnborough at the Rushmoor Community Stadium.
Reece Beckles opened the scoring for the K's in the 20th minute before Farnborough equalised in the 42nd minute, John Oyenuga netting.
Ollie Bailey gave the home side a 52nd minute lead and they kept that until a manic final minute that saw Dan Bennett equalise, only for Charlie Allen to win the game for the Hampshire outfit.
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