Rookie Knapp takes one-shot lead at CJ Cup Byron Nelson
The 29-year-old American fired a seven-under-par 64 to stand on 14-under 128 after 36 holes at TPC Craig Ranch in McKinney, Texas.
"For the most part hitting it pretty solid and keeping in the right areas," Knapp said. "Made it relatively easy on myself. Never really felt like I had to scramble or anything like that."
England's Matt Wallace, who led after an opening 63, shared second on 129 with American Troy Merritt, who closed with a 16-foot eagle putt at the par-5 ninth to fire the day's low round of 62.
World number 56 Knapp won his first PGA title at February's Mexico Open and says he is not nervous about being in contention.
"I feel comfortable. I've been there before," he said. "Courses like this where scores are going to be low you don't worry too much about what other guys are doing. You try to make a bunch of birdies. If I just keep doing the things I'm doing I'll be in a good spot."
Knapp, a back-nine starter, sank an 11-foot birdie putt at 14 and reeled off three birdies in a row with a 30-foot birdie putt at 16, followed by another from just outside 18 feet at the par-3 17th and a two-footer at the par-5 18th.
"Just put a little bit more of a premium the last couple weeks on green reading," Knapp said. "Nice to see a few more going in."
After a three-putt bogey on the third, Knapp answered with a 32-foot birdie putt on the par-3 fourth and a two-footer at the par-5 fifth, a 16-foot birdie putt at the par-3 seventh and a tap-in birdie at the par-5 ninth after reaching the green in two.
"Scores are going to be low," Knapp said. "Just got to keep the pedal down and keep trying to make birdies."
Two years ago, Knapp was working as a nightclub bouncer before going to a developmental tour in 2023 and earning a PGA Tour berth this year.
"Even when I was doing any of that stuff I always knew this was what I wanted to do," he said. "Just kept working away and sticking at it."
Wallace had four birdies, an eagle and a bogey. The four-time European Tour winner seeks his second PGA triumph after last year's Puntacana Championship.
"Really stuck in there well," Wallace said. "Hitting the ball great off the tee. My long iron play can improve a little bit, but I still hit some really nice shots."
Australia's Jason Day, the defending champion, fired a 70 to make the cut on the number at 136.
Three-time major winner Jordan Spieth, who can complete a career grand slam by winning the PGA Championship in two weeks, fired a 70 to miss the cut on 138.
English 16-year-old amateur Kris Kim made the cut on 135 after shooting a 67, a birdie at 18 moving him off the cut line.
He's the youngest player to make a PGA Tour cut since 16-year-old Kyle Suppa at the 2015 Sony Open in Hawaii.
