The second week of the 2018 U.S. Open is underway and those remaining in the main draw are duking it out for a spot in the semifinal. But the players aren't the only ones logging long hours on court: The line umpires have been making calls since the qualifying rounds of the tournament started two weeks ago.
"We're there when the ball lands that close to the line, in or out, and we have to make the call. It's a very intense concentration job," says line umpire Kevin Ware, who has been officiating full-time ever since he quit his job as a web designer five years ago. And by the end of the tournament, "everybody has put in a lot of miles of walking and made a lot of calls."
As an umpire, you never know how long or short your day is going to be, and that's one of the hardest parts of the gig, Ware tells CNBC Make It: "We will go as long as play goes. So if every match goes three sets, we could be here until 10 o'clock or 11 o'clock. We'll keep shifting with the other crew, hour by hour."
There are two crews of umpires assigned to each court. The first shift starts at 11 a.m. when play starts, and the crews will alternate working hour-long shifts until every match on their court is finished for the day.
Rain delays can lengthen the day even more, adds Ware, "but we've trained for this."
After each shift, Ware and his crew head back to their locker room to "rest and do what we need to do to take care of ourselves so that we can get through all of our matches for the day and make as great of calls at the end of the day as we made at the beginning of the day," he tells CNBC Make It.
While some days aren't going to finish until well past 5 p.m., others are short, Ware says: "I've had long days and I've also been able to go see a [Broadway] show on a given night."
And he wouldn't trade the long days for anything: "I love my job. I have the coolest job. When people ask me what I do and I say I'm a tennis official and I'm a line umpire at the U.S. Open I always get a look. And I love that because how many people can say that? Not many."
Plus, says Ware, "we get the best seat in the house."
Like this story? Subscribe to CNBC Make It on YouTube!