 Other than the color they're painted, every basketball court in the NBA is the same. The layout doesn't change from Detroit to Philadelphia to LA. But pretty much every baseball field that has ever been made is unique in some way, and not just the stadium but the actual layout of the field itself. Now it is true that most things in fair territory are closely monitored. Every mound is 10 inches high, but everything outside the foul lines is still largely in play and can't affect the game. This is where ground rules enter the equation. Ground rules are rules that change from field to field, making clear what happens in situations that are unique to each of them. Some ballparks have roofs and catwalks that the ball can bounce off. Some have speakers that are close to the field. Lots of them have fences around them made of different materials, and it's not always clear if the ball hits one part of the fence or another what is in play and what isn't. Take for instance the height of the outfield fence at Boston's Fenway Park. It varies as it goes around the outfield. In left field is their famous green monster, where the fence is a little over 37 feet high, but in center field it drops down to about 17 feet. Where the two walls meet, however, could cause some confusion. So they've drawn a yellow line to mark where one wall ends and the next begins. Because of course it's no guarantee that a home run won't bounce back onto the field or a ball off the monster won't deflect over the fence, hence our ground rules. Which, in Fenway's case, say that if a ball hits to the right side of this yellow line it's a home run, regardless of where it bounces after that. A ball that hits to the left side of the line and bounces back onto the field is still in play. However, a ball that hits to the left side of the line and bounces into the stands is a home run. Every major league team also shares some uniform ground rules. One is that no matter which park a player is at, he cannot go into a dugout to catch a ball. Now he can lean over the railing and if he catches the ball and falls in, then that's fine, but he cannot hop over the fence first and then make the catch. If you want to know more about one team's specific ground rules then there's a page at mlb.com backslash ground rules that has pictures and even some videos of every role and unique aspect of all the fields.