U.S. Open at Oakmont is testing the world's best golfers like few tournaments do. Here's how the cut line works at golf's toughest major.

If scores hold after the second round of the U.S. Open on Friday—and obviously they won't—the cut line is projected to claim anybody shooting worse than three over par.

Two rounds of the U.S. Open are (almost) in the books, and it has been as difficult as advertised so far. The vast majority of the field shot over par in the first two days, with only a handful of players ending Friday under par.