This part here it's gotta be appendage D. What you have is appendage B. There should be a letter kinda near where you put the screws in.

[He moves his gaze back to squinting to read the directions for the cage. In theory, it made more sense to buy it and assemble it. Sure made it easy taking it into the apartment and up the stairs. ...do they have a policy on pets here? Larry didn't think about that. Then again, too fucking late now.]

Says that you gotta put those into the piece that looks like a barbecue grill.

[At least no one has to do it alone...right?]