This practice is one that I've been mulling for a while. Recently I saw a player, Brian DeMars put it into use at an event, and decided that it was a good time to write about it.
At larger events like SCG Opens and GPs it is inevitable that some number of players have to use the restroom when the round is ready to turn over. Maybe they were playing in one of the last few matches of the round. Perhaps they kept walking by the restroom and saw a ridiculous line, and they've chosen the beginning of the round to try to snipe an open stall. Or it could just be that nature calls at that particular moment.
In these situations, players are instructed to seek out a nearby judge and tell them of the situation. If you don't, you're risking Tardiness infractions. While it sucks to issue a Game Loss to someone who was taking care of a natural biological function, we can't let the excuse "I was in the restroom" slide because this is such an easy lie to tell. Or not even lie at all; if you're late coming back from a smoke break, just stop by the restroom and you're technically telling the truth.
It used to be that when a player came to me with this situation, I would write their name down, go to their match, and inform the opponent of the situation, sometimes sticking around until the player arrived in order to issue a time extension. That's a fine practice time permitting, but that isn't always the case, and if the judge can't make it to the match, that's when things get complicated.
As soon as the round starts, the opponent is going to call for a judge and be told that he wins game one. Then the player is going to return from the restroom, call for a judge, and explain where he was. That's when the question is asked:
"Which judge did you talk to?"
Since the average player can't name the average judge, this leads to an awkward stand off where the player is scouring the hall looking for that person he talked to five minutes ago. I actually had this happen to me, and eventually had to take the player's word for it that he had spoken to a judge. The opponent was not happy about the lack of a free game win.
Enter Brian DeMars at SCG Cleveland. When he had to go to the restroom, he came up to a cluster of judges, and one of them took point of the conversation. After getting the ok to go, Brian asked for the judge's name and wrote it down on his life pad. It's such a simple thing, but it revolutionizes this whole interaction. Instead of putting the onus on the judge to hunt down Brian's table, Brian can simply arrive at the table, call for a judge and say that "Judge X ok'd it." From there it is a much simpler verification process.
Players, get judges's names. Judges, give your name out (and make them write it down) when you give the okay for a restroom break.