England's Harry Hall holed four birdies midway through his round to maintain his three-shot lead after two rounds of the Charles Schwab Challenge in Texas.
The Cornwall man followed his opening round of 62 with a four-under-par 66 at Colonial Country Club to move to 12 under, three clear of Harris English.
The highlight of English's round of 66 was a hole-in-one at the eighth.
However club professional Michael Block finished bottom of the leaderboard on 15 over and missed the cut.
Block had earned an invitation after tying for 15th at last week's US PGA Championship but did manage to improve on his opening round of 81 by seven strokes.
"I've enjoyed every single moment. But it is what it is, and I'm moving on," said the 46-year-old Californian who has a sponsor's invite to next month's Canadian Open and will also try to qualify for the US Open.
Former Walker Cup star Hall, 25, turned professional in 2019 but is in his first season on the PGA Tour and chasing his first win after chalking up two top-10 finishes so far.
Starting at the 10th, the world number 197 bogeyed the 13th before getting that shot back two holes later and grabbing four straight birdies from the 17th to maintain his position at the top of the leaderboard.
That run was ended with a bogey at the third, but he birded the seventh and holed his second attempt to escape a greenside bunker at the eighth.
English fared much better at the 170-yard eighth where he produced the first ace at the hole since Jim Furyk in 2011.
Argentina's Emiliano Grillo is a shot behind English after carding the day's lowest round of 65 while Adam Schenk, Byeong Hun An and Robby Shelton are tied for fourth, a stroke further back.