If the holes where the cable goes into the frame are big enough for the housing to go right into the frame, then the housing will have to go right through. Do you have cables going through now or are you rebuilding a bike with no rear brake. If the former, tie a string to the cable before you pull it out, so you can pull the new cable through. If the latter you will have to lead the way through with an straightened coat hanger wire, with the string tied to it.