Chicago -- Oh, the lengths people will go for a baseball.

If you've ever stood at the corner of Waveland and Kenmore during a Cubs game, you have an idea. That's where the ballhawks -- the prowling folks who will go greet lengths to catch a nine-inch, five-ounce tightly woven ball of yarn -- call home.

But you probably don't know the ins and outs of what it takes to be a ballhawk and go for the pearly white ball with red stitching and blue print that reads Official Major League Baseball.

It takes blind dedication. The ballhawks go to all 81 home games, plus travel to Spring Training.

It takes knowledge of the game. They study hitters' charts and tendencies against opposing pitchers, play the conditions, including weather and wind, listen to the game on the radio and wear sunglasses to shade what they see.

It takes an uncanny passion for baseball, and an understanding that the game is timeless. Days will pass without a ball reaching the street. They certainly don't do it for the fame.

Still, as one ballhawk put it, "This is a wonderful life."

Ballhawking is as old as Wrigley itself, though the tradition hasn't received as much attention as the ivy-covered walls or hand-operated scoreboard. The ballhawks have roamed the streets beyond the Friendly Confines since the stadium opened in 1914, thanks to the perfect catching conditions. The stadium's brick facade used to be only about 15 feet high, but that was before the 2006 bleacher expansion. Still, even with the extra rows pushing back further, roughly 400 balls cleared the stadium in batting practice last year and 15 made it out during games, according to one ballhawk.

There was probably nothing like the 1998 season for the ballhawks, when Sammy Sosa and Mark McGwire were chasing home run history. Back then, as many as 200 people would crowd the streets to catch one of the historic balls. But there's a group of six or eight dedicated ballhawks -- Moe, Ken, Rich, Dave, George and Andy -- who have been through it all.

Moe Mullins, 59, of Chicago, has been ballhawking since 1958. The self-described "king" has caught more than 5,400 baseballs, including 54 home runs and five grand slam homers, which he now stores in fish tanks for display.

But even with Mullins' experience, he couldn't accomplish what Ken Vangeloff did. Vangeloff, 47, is the only ballhawk to catch a ball from both Sosa and McGwire in '98, snagging Slammin Sammy's 14th long ball and Big Mac's 48th dinger of that season.

Since moving to Chicago in 1990, Vangeloff has caught more than 3,000 balls.

"If there is a goal or an achievement -- kind of like 3,000 hits gets you in the Hall of Fame -- I wanted to make sure I got 3,000 balls," he said.

At some point, there's a certain amount of luck that comes along with being a ballhawk -- being in the right place at the right time, a veteran will often have a ball roll right into their lap. But after spending years roaming the streets, the ballhawks turn into automated home run-catching machines.

"I know they're good," said Taglia, who has been watching the ballhawks from his rooftop bleacher company for the last five years. "They play the ball, they play the wind, and they're actually pretty right on. There might be 100 people right here, and the ballhawks are usually the ones who get the ball. So they're good, they know what they're doing."

One ballhawk observer said most ballhawks take an extra eight or 10 steps before the "average" fan gets a bead on the ball. The ballhawks stand on the curb next to the fire hydrant and look up at the Wrigley Field press box, hoping the tiny white dot in the distance flies about 380 feet into their glove.

It's hard not to notice the ballhawks when you walk around outside Wrigley Field, before, during or after a game. Sometimes people like Lori Silvestri get so intrigued they decide to hang out with the ballhawks. Silvestri has spent parts of weekend home series for the last three years trying to catch a home run ball.

She has been unsuccessful, though she refuses to use a glove. What's Silvestri going to do with her ultimate souvenir when she catches it?

"It's going to be something I put on my dresser at home, and I'm going to look at it everyday and just be excited," she said. "And pray that, one day, be able to say that this is the ball that won the Chicago Cubs the World Series in 2014. Or something close to that, while I'm still alive."

Probably no one knows more about the balhawks than Mike Diedrich, the producer/director of "Ballhawks," a documentary narrated by Bill Murray. Diedrich filmed for the better part of the 2005 and 2006 seasons, compiling more than 300 hours of footage.

Diedrich filmed "Ballhawks" with no financial backing and a donated camera. He got Murray to do the voiceover as a favor to Joel Murray, Bill's brother and the film's executive producer. The documentary also features former Cubs third baseman Ron Santo.

Asked to tell Cubs fans why they should see the film, Diedrich offered an inspirational response: "It's a story about relationships and doing what you love," Diedrich said. "Gosh, there's nothing better than being at Wrigley Field on a warm summer night with the wind blowing out and just having a Cub game. If you're a Cub fan, it doesn't get much better than that."

"Ballhawks" will premiere in Chicago at the Gene Siskel Film Center on May 28-30. Tickets are available at the Siskel box office and via Ticketmaster for $10.