Kleinveldt was the star of the show with bat and ball for the County on day one.
The South African ace top scored with 43 from 63 balls as Northants were dismissed for just 194 after Nottinghamshire elected to field.
Kleinveldt then set about preserving his side’s lead, taking four for 34 as the opposition were reduced to 80 for five.
And the all-rounder is now hoping Northants can stay ahead going into the second innings.
“The wicket is obviously doing quite a bit and we’ve done well to scrape 190 - it’s a competitive score on this pitch and hopefully we nail in a lead,” Kleinveldt said.
“It’s definitely a top-of-off length you have to hit consistently. When they bowled straight it was very tough to get away and we learned from that.
“I told myself I don’t mind getting driven, the batsmen are tentative and you’re always in the game.”