The space between the testicles and the anus that takes the brunt of the pain during particularly violent episodes of defecation. A reference to the common structure found in the launch pads of the space shuttles.
Larry: "Aww man after that Mexican food last night my flame trench hurts like hell."
Matthew: "Dude mine too. I didn't even eat Mexican food!"
Larry: "Oh yeah... about that... I meant to tell you before now, but last night you got blackout drunk and let that gay guy go to town on you."