"What" does he know that I do not know?"
Would I R-K it thusly:
(1) The first line: He does know what.
(2) Second line: I do not know that.
(a) Attach "That" with a dotted line to "what."
Sorry. I tried to post the diagram, but I am getting rusty. It sounds to me, though, as if you understand how to do it.
Thanks a million for the confirmation.
If learners only realized what they are missing in not using Reed-Kellogg.
Forcing oneself to map a sentence is the exact kind of discipline that everyone
-- including native speakers -- needs.
I think that one person was quoted as saying something like: Don't write it if you
cannot diagram it.