Sentence:  If the <WSD>soffit</WSD> is to be sloping, simply attach the <WSD>soffit</WSD> board(s) to the underside of the rafters, butting the edges tight against the fascia board in front and the barn siding in the back. 
Meaning of the word marked with <WSD> tags:  The visible underside of an arch, balcony, beam, cornice, staircase, vault or any other architectural element.