Bryce Harper drew some attention Saturday when he intentionally (and repeatedly) scuffed the Braves logo that had been imprinted in the dirt behind the plate at Turner Field in Atlanta. On one hand, it was just a bit of gamesmanship, intended to get Atlanta’s goat. On the other he was clearly disrespecting the home team. Ultimately, the gesture was so minor that it should serve as fuel for Braves fans, but not the Braves themselves.

It did bring to mind, however, an interesting piece of Code which might be the single most arcane and widely followed, both at the same time. While other antiquated unwritten rules, like “Don’t swing at the first pitch after back-to-back homers” have fallen nearly entirely off the map, this one, while just as quaint, continues to be ubiquitous. Harper himself was following it, even as he set about being bratty to the Braves.

It’s a simple one: Don’t walk between the pitcher and the catcher when you’re going up to hit—walk around. This almost never causes a commotion, because it’s almost never done. It’s as close to instinctive on the baseball landscape as the unwritten rules can get.

“It’s just bad etiquette to walk in front of the catcher,” said former A’s infielder and current A’s analyst Shooty Babbit. “It’s like breaking the rhythm of the game. You want to creep into the batter’s box; you don’t want to create any attention. You don’t want to give them any more incentive to get you out.”

Dusty Baker learned about it from Hank Aaron when he was coming up with the Braves. “He taught us to walk behind the umpire all the time,” he said. “Not so much for the rhythm of the game, but that it’s their territory, not yours.” Baker talked about the action showing respect for both catcher and umpire.

A poll of current major leaguers would probably draw more blank stares than anything, but one would be hard-pressed to find a guy who makes a practice of doing anything else.