In Backyard Baseball, it is almost impossible to hit a homerun without the help of the Aluminum Power bat powerup. However, there is still a chance that the Aluminum Power hit will not leave the ballpark. There's a large apartment complex in left field that will knock the ball down, there's a trailer in center field and two dumpsters in right center field. Unlike Steele Stadium where hitting off the shed is a homerun, there's almost no way to hit an out of the park homerun. Usually if the ball is stuck on top of the dumpster or trailer, then a ground rule double is ruled (unless if it's the Gameboy Advanced version, it counts as a home run)...it isn't uncommon for the game to freeze at this time either such as if you have a player cross home plate (meaning they can't go back because of a bug in the game). The center fielder also doesn't have much room, as they play their position really close to the shortstop and 2nd base.
It appears that there is a second location of tin can alley, as there's now a clear fence in the back end of the field, so it's not the same field as the kids use for baseball.