JAY Z & EMINEM PERFORMING ON A ROOFTOP FOR THE LETTERMAN SHOW!

After selling out their upcoming concert at New York's Yankee Stadium before tickets even officially went on sale, Eminem and Jay-Z took the stage on the "Late Show With David Letterman" Friday night. The two veteran MCs are promoting their co-headlining hometown stadium performances in Detroit's Comerica Park and Yankee Stadium this September

Eminem, sporting a black jacket, jeans and a white shirt, began by presenting the comedic "Late Show Top Ten" list segment featuring his "Pieces of Advice for the Kids."

"If I sign something for you and I see it on eBay, when you go home, I'm gonna be under your bed," Eminem joked, struggling to keep a straight face. He continued with, "Always purchase music through authorized retailers that pay royalties to the artists," and "Remember the magic words: 'Please,' 'Thank You' and 'Step Off Bitch.' "

Jay-Z followed Em by sitting down and chatting with Letterman about his and the Detroit MC's working relationship. "We did a song on my album called Blueprint — the first one, I've got a lot of them — called 'Renegade' and it was good," Jay said. "When you make good songs, you become friends."

Letterman then asked why the pair are just deciding to tour together now.

"Em is a notorious non-tourer," said Jay.

Later, Hov almost argued the positives of NBA baller LeBron James leaving the Cleveland Cavaliers and joining the New Jersey Nets, which the rapper co-owns, before stopping himself.

"There's rules and guidelines that I want to be very certain to follow," Jay told Letterman. "Everyone would love to have a LeBron James on their team. He's a free agent come July 1. We're gonna try after July."

Letterman disagreed with Jay's interest in James, saying, "If LeBron James wants to be a guy, he will stay where he is and not cut the heart out of that city by leaving Cleveland." At press time, the basketball player's decision is still anyone's guess.

Then Jay and Eminem's pre-taped performance rolled. The gents played three songs with a live band, opening with Eminem's latest single "Not Afraid" before moving into Jay's "On to the Next One" from 2009's The Blueprint 3. As a grand finale, the pair performed "Renegade," their first collaboration from Hov's 2001 album The Blueprint. The mini-concert was originally filmed earlier this week atop the Ed Sullivan Theater.