Oh, I see.

After taking a closer look, it appears that the RNC run is right up against the wood trim to look nice and neat.

Then when you went to install the LB it wouldn't sit flush up against wall.

Been there, done that. In fact the same thing happened to me yesterday while doing a service but I caught onto it before I glued the pipe.

I have to get a digital camera so I can start posting some of my work.