England's Ashley Chesters held the clubhouse lead after day two of the weather-affected Porsche European Open in Hamburg.
Chesters and fellow Englishman Jordan Smith were tied at the top of the leaderboard on eight under par when a second heavy downpour of the day forced play to be halted due to a waterlogged course.
But when play resumed almost four hours later, Smith bogeyed his final hole of the day - the ninth - and Chesters picked up a shot at the eighth on his way to a second round of 67.
That gave the 27-year-old a nine-under-par halfway total and one-shot lead over Bangladesh's Siddikur Rahman, with Smith a shot further back after his own 67.
Paul McBride is the best of the Irish on three under, but he only got to play 13 holes in the second round. Paul Dunne is two shotes worse off after he complted 16 holes.
"I definitely didn't hit it as well off the tee today but the putter made up for a lot, so that's always nice," said Chesters afterwards, who turned professional after helping Great Britain and Ireland to a record Walker Cup victory at Royal Lytham in 2015, where he won three-and-a-half points from his four matches.
The world number 446 gained his European Tour card via the qualifying school in 2016 and has missed seven cuts in 14 events this season, with a best finish of joint eighth in the Hassan Trophy.
"(Leading) is a completely new experience so tomorrow is going to be totally new to me," Chesters added. "The whole year has been a learning experience really so hopefully I'll learn something again tomorrow, whatever happens."
Smith finished top of the Challenge Tour rankings in 2016 and is currently 42nd on the Race to Dubai, having already earned enough money to guarantee another season on the European Tour.
"I'm loving the course and playing good so have just got to go into the weekend and give it my best," the 24-year-old said. "I was in a good flow and would have loved to have got my last two holes done and dusted (without the delay), but you can't really help the weather.
"I had a good year last year and the target for this year was just to keep my tour card. I managed to do that pretty quickly, which was nice, so the next aim is to win an event."