Fourth hour, rook endgame, both players shuffling on the increment, and neither will be the one who admits it is over. In a rated event that game does not go on forever. An arbiter has been standing behind the board with a scoresheet for a while, and at some point he stops the clocks and writes ½-½ himself.
Article 9.6 gives him two triggers. Five appearances of the same position, counted the same way as threefold repetition. Or seventy-five moves by each player with no capture and no pawn move, counted the same way as the fifty-move rule. Either one, and the game is drawn.
Automatic means automatic
No claim. No scoresheet held up. No option to say you would rather play on. The half point lands on both players whatever they think about it, which is what makes these rules different from the two they are built on.
There is one exception, and it is the sensible one. If the move that completes the count happens to be checkmate, the mate stands. You do not save a lost game by pointing at a counter.
Why they were added
The Laws worked for decades on claims alone, and mostly that was fine. It broke down in two places.
The first was the stubborn player: a competitor grinding a dead position for another hour, hoping his opponent’s flag falls, with no obligation to claim anything. The old rules gave the victim a way out only if he kept a perfect scoresheet, which is exactly the thing that goes wrong when you are down to two minutes.
The second is that a rule based on a claim cannot be applied by anything except a human. An automatic limit can. Since the 2014 edition of the Laws every game has a hard stop written into it, which is also how a chess server can end a game correctly without asking anybody.
What it means for your game
Almost nothing, and that is the intention. If you are the one making progress, keep resetting the count: a capture or a pawn move puts it back to zero and you have a fresh seventy-five, though your opponent can still claim at fifty. If you are the one defending, remember which rule is yours. Fifty is a right you have to exercise, and it is your fastest route to the half point. Seventy-five is a backstop that only matters when both players are asleep.
The one place the numbers really bite is a long technical ending where you know the win but not the shortest route. That is a good argument for spending an evening on rook endgames rather than another opening video, and for asking what an arbiter is actually there for before your first tournament rather than during it.