ST. PETERSBURG -- Tropicana Field has already hosted history this season, as the Rays' home dome was the site of Major League Baseball's first instant replay usage (Sept. 3) and the first overturned call (Sept. 19).

Come Thursday, the Trop will again enter into uncharted territory as the Rays will take their home turf for a franchise-first playoff appearance in the American League Division Series.

complete postseason coverage

While talk has ceased about whether the AL East champion Rays are for real, Tropicana Field is a different story. The quirky dome has tarps covering the upper level, keeping the capacity at a mere 36,048. The artificial turf and white ceiling are common criticisms, but the four catwalks that hang from the ceiling are arguably the biggest nuance of the dome.

Quirky? Yes. Fair? Hardly. The catwalks have contributed to several game-changing moments already this season. Just ask the Twins, who saw Sept. 20's game at the Trop take a turn for the worse.

The game was still scoreless with two outs in the third inning when Twins starter Kevin Slowey was facing Carlos Pena with runners on first and third. Slowey got Pena to lift a high popup down the first-base line. But the ball struck one of the roof's catwalks on its descent, sending it back toward home plate, where Joe Mauer made the catch. The ball was ruled to have hit the catwalk in foul territory, meaning it was a dead ball. Pena made use of the break, drilling a line shot to the right-field wall for a two-run double. The play gave the Rays a 2-0 lead, en route to a 7-2 playoff-clinching victory.

But the ball doesn't always bounce the Rays' way. The same catwalks nearly cost the Rays the game in June 31's narrow 5-4 win over the Red Sox.

Boston's Brandon Moss lifted a fly ball into right field that should have been the ninth inning's second out. Instead, the ball hit the "B" ring catwalk and was ruled a double, much to Rays closer Troy Percival's dismay.

It's frustrating to know that has a part in the game," Percival said. "That's just a joke. They've got to come up with something better than that. I'd hate to see something like that cost us. I haven't seen us benefit a whole lot from it. I throw a pretty good pitch, get a popup on a changeup, and the next thing you know you've got people running around the bases."

Which way the catwalks will swing in Thursday's series opening game against the White Sox is anyone's guess.

"The catwalks to me are kind of a coin flip," Rays right fielder Gabe Gross said. "I don't think they are going to come into play as far as missing a ball or not. ... To me, it could be us [that benefits], could be them."

The four catwalks are part of the support structure and are lettered, with the highest inner ring being the "A" Ring, out to the furthest and lowest, the "D" Ring. In 11 seasons, 96 fair balls have struck the catwalks -- 11 this season, including nine by players on opposing teams.

According to official League rules, if a batted balls strikes either of the lower two catwalks, lights or suspended objects in fair territory it is a home run. A fair ball that is not deemed a homer and doesn't come down is awarded two bases.

"It's awkward," Boston's manager Terry Francona said after witnessing Moss' ball drop while Gross watched helplessly in the outfield. "All of a sudden, the ball, nobody knows where it is, and we've got a chance to win the game. ... A crazy play, and you'd rather not see balls hit things like that. But if it's going to help us, we'll take it."

So will the Rays, who enter Thursday looking to build on a Major League-best 57-24 home record.

"Game 1 or 2 for us, in my eyes, are must-win," Rays rookie Evan Longoria said. "It's going to be close to impossible if we go over [to Chicago's U.S. Cellular Field] and we are down, 0-2. I mean, home-field advantage is what it's there for. You are supposed to win."