Waveport assignment in hfss

HI,
I want to know the waveport assignment for a rectangular waveguide(RWG) model designed considering thickness.
without thickness ,we can draw a rectangular waveguide and select face and assign waveport and simulated.but for a waveguide modelled using thickness how to assign waveport.
Can i draw a rectangle over the inner dimension face of RWG and assign waveport on it.should i draw rectangle over the outer dimension??.

thankyou

For transmission line structures entirely enclosed in metal, port size is merely the waveguide interior carrying the guided fields, so its over the inner dimension.