George Coetzee kick-started his bid for a second Tshwane Open title with a 64 that gave him the midway lead at Pretoria Country Club.
The 2015 champion grew up playing the Waterkloof layout and after an opening 67 had left him in the pack on Thursday, he used all his local knowledge to get to 11 under and surge up the leaderboard.
His bogey-free effort left him a shot ahead of Finn Mikko Korhonen - who matched his 64 - and Chile's Felipe Aguilar who shot a 67.
The trio posted their scores in the morning session and while conditions remained perfect in the afternoon, none of the later starters could make a major move.
Overnight leader Louis de Jager was at seven under alongside countrymen JC Ritchie and Justin Walters, and Portuguese Ricardo Gouveia.
All three of Coetzee's European Tour victories so far have come on African soil and he was happy with his work so far as he looks to make it four.
"I’m happy to have posted two pretty good rounds," he said. "I’ll try and just focus on playing decent golf and posting good numbers for the weekend.
"It was a nice stretch on the back nine - my front nine - where I got a couple of birdies in a row.
"On the front nine - my back nine - I felt like I played pretty well, I just didn’t get the ball in the hole but I guess that’s the way golf works.
"My short game feels good and it keeps me in the mix."
I’ll try and just focus on playing decent golf and posting good numbers for the weekend - George Coetzee
Aguilar lost his card last season but regained it at the Qualifying School to make it 11 uninterrupted campaigns on the European Tour, although he did miss his first three cuts in 2018.
Korhonen, meanwhile, was a runner-up here last season and is looking for his first European Tour title.
Aguilar picked up birdies on the third, fifth and seventh before eagling the par five ninth to get to 11 under and lead by one from Coetzee at the turn.
The South African - who started on the tenth - made four gains in a row from the 12th and added to them on the 17th and 18th.
Korhonen had birdies on the 12th, 13th, 14th, 16th and 18th and, while he dropped a shot on the first, he regained it at the third.
A run of pars followed from the three leading contenders but a poor second shot left Aguilar in a nasty lie on the 13th and his chip went a long way past the pin to lead to a first bogey of the day.
Korhonen then put his approach to the par five ninth to five feet and made an eagle to make it a three-way tie at the top.
Aguilar got his nose in front with a birdie on the 15th but Coetzee put his tee-shot on the par three eighth to four feet to join him at 11 under.
Two-time European Tour winner Aguilar found sand off the 18th tee to surrender a second bogey of the day and drop alongside Korhonen.
Ritchie posted a 67, Gouveia and Walters both signed for rounds of 68 and De Jager carded a 71.
South Africans Thomas Aiken, Christiaan Bezuidenhout, Combrinck Smit and Erik van Rooyen, Scotland's Scott Jamieson and Frenchman Clément Sordet were six under.
Major champion Danny Willett was at four under after a 68 - his first sub-70 round since returning from a shoulder injury - had him on course to make a first cut of the season.
