Take the bill and fold it three times over. Slide the cash, a $20 payment or more, underneath the belly of your nosebleed ticket. Place the wad into the pit of an empty pocket.

You don’t want to stumble when greasing the palms of an usher at the U.S. Open in Flushing, Queens. Indeed, the Grand Slam event is considered by many frugal sports fans to be New York’s premier institution still operating on the winks of dead presidents.

While many courtside seats are sold out – and can cost as much as $350 or more – that doesn’t mean those same seats aren’t still available, and for cheaper. On two courtside missions over the Labor Day weekend, I was able to score a box seat at the Open for as low as $48 by purchasing the cheapest seat available in Arthur Ashe stadium – an airy perch where you could not tell the difference between Serena or Venus or Mars – then easing courtside by slipping an amiable usher a crisp Andrew Jackson.

During one performance, I was also able to enter Arthur Ashe without showing a ticket at all, breezing by security guards and ticket takers with nothing more than a casual nod, then taking a seat only a few rows away from celebrity enthusiasts like former Mayor David Dinkins and former “Saturday Night Live!” comic Jon Lovitz, no stranger to palm grease himself.

Years ago, Lovitz told me, he and five friends were given sky-high seats. When they asked an usher how much it would cost to inch closer to courtside, the fee was $100 each.

“Not too cheap,” Lovitz said, but far cheaper than the tickets’ face value. He and his agent paid it without thinking twice.

Now, as a tournament guest, Lovitz is privy to most areas, but should an usher find him a choice seat, he tips.

“It’s the right thing to do,” the actor said,”[the ushers] are providing a service.”

Not according to tournament organizers, who in recent years have been looking to crack down on the flow of palm grease. The tournament’s senior director for public relations, Chris Widmaier, said he knew of three ushers who had been fired in recent days for accepting “tips” for “seat improvements.” According to Widmaier, the tournament has also hired “secret-service like” employees who attempt to deliver bribes to ushers, then report the incidents.

The bribes, considered a second-degree misdemeanor that can bring a $1,000 a fine and potential one-year prison stint, are rarely prosecuted. A spokesman from the Queens district attorney’s office said that not one usher has been charged with “commercial bribery” in recent memory.

Peter McLaughlin, a representative for Local 176 of Licensed Ushers and Ticket Takers, a union that provided over 200 ushers and ticket takers at this year’s Open, said he knew of only two ushers who had been fired so far this year for accepting money for seat improvements, compared to four in 2003, and seven in 2002.

“It doesn’t really happen so much anymore. We forbid it and caution all our members about it,” McLaughlin said. “What you’re seeing now is the end of an era.”

And what an era it must have been.

“Forget about it, the Open was like Rome, everybody was eating,” said one former facility operator, who claimed to have devised a scheme 10 years ago whereby non-ticketed “clients” would whisper code numbers to gate keepers and enter unfettered. The cash would then be slipped into this former employee’s palm in front of the press box, where absent seats could fetch upwards of $500.

The reason the Open is so ripe for greasing is simple economics, ushers said. Open fans tend to come from higher income brackets and the tournament lasts only two weeks: It is a crazed time that lends itself to a transient-like environment.

One usher, speaking on the condition of anonymity, defended underpaid employees – they earn about $100 a day – who accept money to fill seats that otherwise would go empty. The usher said that the “corporatization” of the Open, where companies purchase clusters of high-priced boxes that often go unused, has relegated blue-collar fans to nose-bleed status. So, the usher asked, what’s so wrong about giving some fans the opportunity to see the balding Andre Agassi return a serve up close?

For this reporter, bribing an Open usher was not an entirely new experience. I first tried my hand three years ago for a five-set nail-biter between Tim Henman and Richard Krajicek. I remember marching down to the lower tier, a wedged Jackson peeking out from behind two stubs, then nervously handing it all off to a grandfatherly man with thick glasses who showed my sister and I a pair of picture-perfect, courtside aces.

Getting up close in the post-9/11 era was a more challenging mission. So many guards. So many ticket takers. Squinting at the blurry baselines on the green hard court on a recent night from my seat in Row V, Section 313,it seemed impossible.

Walking around – and getting down to the lower tier by nonchalantly ducking into an employee-only elevator – I studied the ushers’ faces. Who would be most likely to take my money? The younger types with sporty sunglasses and groomed goatees seemed less daring: Stay away, I noted. But the trusty, pot-bellied veterans, the ushers who seemed to carry an old-world worn sense of disdain towards Open blue bloods seemed the most grease-able. I made my approach.

“Can you help me find my seat?” I said to one, spotting him alone between games.

He glanced at the ticket in my hand, that green paper burning underneath, and stared me down.

“You a setup guy?” he said.

Nah. Just a fan that wants to tell the difference between Venus and Serena.

“You sure you’re not a setup guy?”

No sir.

And with one last look, my new friend palmed my bill and escorted me to a lonely courtside box. The purchase also came with instructions: how to get in again, which ushers to talk to, names to drop.

The night was peaceful down there. You could smell the red wine and cologne of a more genteel crowd. You could hear sneakers shuffling on the baseline, not roaring jet planes overhead. You could also see the faces of the players.

It was Venus after all.