BALTIMORE -- Sign stealing has been an accepted part of baseball forever. Even the sport's most iconic moments, such as Bobby Thomson's "Shot Heard 'Round the World" that won the 1951 National League pennant for the Giants, are not immune from rumors of thievery.

But it often falls on one player to prevent that theft: the catcher.

"Anybody who tells you they've never played on a team that peeks at signs is a liar," said Orioles catcher Chris Snyder, a 10-year veteran who said he spends most games studying other catchers. "You just go through little checkpoints and keep an eye out."

Something must have caught the eye of Joe Girardi, a former catcher, in the first inning of Monday's 4-2 Yankees loss to the Orioles. The manager had to be restrained, apparently angry with Baltimore third- base coach Bobby Dickerson over what he perceived as stolen signs.

Girardi didn't address the issue directly before Tuesday night's game, but did acknowledge sign stealing as part of the game. Orioles manager Buck Showalter said the same and that he expects most teams to attempt it. Brian Cashman defended Girardi's actions.

"Our job is to make sure teams aren't doing that," the general manager said. "That's all Joe was doing, so it's part of the game."

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Had Girardi been behind the plate, he could have employed more discreet methods.

Snyder's checklist includes watching to see if a batter is turning his head on certain pitches, and whether a runner is picking at part of his uniform or lifting one of his feet.

"If you have the slightest idea that something is going on," Snyder said, "then you get out there and change the signs."

When asked whether the Yankees would do just that, Girardi said: "We do everything we can to protect our players." He later added: "Signs can't be simple."

The complicated sequencing of signs leads some to consider attempted thievery as no big deal.

"I've heard of a couple of teams that try to steal signs," Orioles catcher Steve Clevenger said. "We're not one of them. The signs are just too difficult these days. It's not even worth the time or the effort."

While the signs themselves are complicated, shielding them isn't.

"You make sure your knees are facing the pitcher," Yankees catcher Austin Romine said. "You know, it's pretty simple."

Snyder said he didn't think Girardi's catching experience left him any more in tune with potential sign theft. The confrontation, he said, was likely strategic.

"A lot of things happen on the baseball field," Snyder said. "But the game does police itself. We're all grown men. It's September. It's a race and it's gonna get heated. So yeah. Great. Light a fire. Give the fans something to enjoy. Why not?"