This thread is starting to get a bit confusing...too many parallel lines!
Jay, I was actually responding to Timbeal's last comment on square rule interchangeability. I found it a bit confusing and was hoping for clarification on his part.

In reference to you last said on snapped lines in square rule Jay, I would agree that snapping lines was not the norm within square rule timber layout as Hodgson describes it. I think that this describes one of the essential differences between North American square rule and Eastern center line layout. The former normally snaps lines only rarely. It is not the essential element or technique. The latter totally revolves around the centered snap line.
Hodgson mentions Bell's Carpentry, which predates his own book. I was thinking about picking up a copy of that, for reference. Has anyone here read it? It would be interesting to reference it for clues as to when snapped lines entered into the square rule system.

Will, would you say that Eastern timber framing uses reduction housings in a similar way to how they are used in square rule? I've really never thought of them used that way.