Ollie Stone demonstrated his batting prowess as he helped Northamptonshire secure a solid first-innings lead in the Second XI Championship match against Sussex at Horsham.
Stone hit 71 and shared an eighth-wicket stand worth 92 with Basil Akram (31) as the County totalled 325 all out - 111 runs in front.
Their efforts built on the foundation laid by overnight pair Christian Davis (47) and Luke Blackaby (55) who posted 114 for the fourth wicket after Northamptonshire resumed on 115-3.
Leg-spinner Will Beer proved the pick of the Sussex bowlers, finishing with 5-85.
But the home side hit back strongly in the final session to close on 181-2 - a lead of 70 with a day to go.
First-innings century-maker Ben Brown contributed an unbeaten 72 while Rory Hamilton-Brown weighed in with 91 before falling victim to Saif Zaib, a 15-year-old left-arm spinner from the Buckinghamshire age-group system.