The cut line is the score after two rounds of a four round tournament that decides who plays the weekend. Everyone at or better than it continues; everyone worse goes home, usually without prize money. Each tour and each major sets its own threshold, expressed as a number of players and ties.
It exists for practical reasons. A field of well over a hundred players cannot be got round in a day at a sensible pace, so the field is halved after thirty-six holes and the weekend rounds run in tighter groups, which is also what makes them watchable on television.
The thresholds differ by event. As of the 2026 season the PGA Tour cuts to the top sixty-five players and ties at most tournaments, the Masters to the top fifty and ties, the United States Open to the top sixty and ties, and both the Open Championship and the PGA Championship to the top seventy and ties.
Missing the cut costs more than a weekend. For most players there is no prize money at all, no ranking points, and travel and caddie costs still to pay. The second round of a tournament is often tenser to watch than the fourth.