The One With Rachel's Phone Number - S9-E9
Visible crew/equipment: In the scene where Chandler pretends that he just got home from Tulsa and meets Joey who is waiting in the hallway outside the apartment, the camera cuts between Chandler and Joey. Every time the camera shows Chandler, there is a wooden wall at the left edge of the screen with an orange tape. This is evidently part of the set, because when the camera cuts to Joey, the wooden wall with the orange tape is nowhere to be seen. (00:16:45)
The One With Rachel's Phone Number - S9-E9
Visible crew/equipment: After Chandler has climbed down the fire escape and shows up in the hallway where Joey's been waiting with a baseball bat, when they both walk into the apartment the opening in the wall can be seen beside the door. We can see the opening again after Joey finds Chandler's suitcase.
Answer: The statements that she's contradicting (that it is common, it happens to every guy, and it's not a big deal), are the things that a woman commonly says to a man who is suffering from erectile difficulty, typically to assuage his bruised ego. However, most men do not believe that these statements are true, as evidenced by Chandler's outburst. He's so caught up in the proof that women are lying about it that he gives himself away.
Rooster of Doom