See the ACL2 documentation topic PROOF-TREE for an introduction to
proof trees in ACL2:

http://www.cs.utexas.edu/users/moore/acl2/current/PROOF-TREE.html

The key bindings set up when you start proof trees are shown below.
See file *note PROOF-TREE-EMACS.txt for how to get started with proof trees.

        C-z h               help
        C-z ?               help

Provides information about proof-tree/checkpoint tool.  Use `C-h d' to
get more detailed information for specific functions.

        C-z c               Go to checkpoint

Go to a checkpoint, as displayed in the "prooftree" buffer with the
character c in the first column.  With non-zero prefix argument: move
the point in the ACL2 buffer (emacs variable *mfm-buffer*) to the first
checkpoint displayed in the "prooftree" buffer, suspend the proof tree
(see suspend-proof-tree), and move the cursor below that checkpoint in
the "prooftree" buffer.  Without a prefix argument, go to the first
checkpoint named below the point in the "prooftree" buffer (or if there
is none, to the first checkpoint).  Note however that unless the proof
tree is suspended or the ACL2 proof is complete or interrupted, the
cursor will be generally be at the bottom of the "prooftree" buffer
each time it is modified, which causes the first checkpoint to be the
one that is found.

If the prefix argument is 0, move to the first checkpoint but do not
keep suspended.

        C-z g               Goto subgoal

Go to the specified subgoal in the ACL2 buffer (emacs variable
*mfm-buffer*) that lies closest to the end of that buffer - except if
the current buffer is "prooftree" when this command is invoked, the
subgoal is the one from the proof whose tree is displayed in that
buffer.  A default is obtained, when possible, from the current line of
the current buffer.

        C-z r               Resume proof tree

Resume original proof tree display, re-creating buffer "prooftree" if
necessary.  See also suspend-proof-tree.  With prefix argument: push the
mark, do not modify the windows, and move point to end of *mfm-buffer*.

        C-z s               Suspend proof tree

Freeze the contents of the "prooftree" buffer, until resume-proof-tree
is invoked.  Unlike stop-proof-tree, the only effect of
suspend-proof-tree is to stop putting characters into the "prooftree"
buffer; in particular, strings destined for that buffer continue NOT to
be put into the primary buffer, which is the value of the emacs variable
*mfm-buffer*.

       C-z o                Select other frame
       C-z b                Switch to "prooftree" buffer
       C-z B                Switch to frame called "prooftree-frame"

These commands move between buffers and frames, as indicated.  The
first of these has nothing specifically to do with proof trees, but is
handy if you have at least two emacs frames displayed.  The second
takes you to the "prooftree" buffer (in the current frame), while the
third takes you to the frame called "prooftree-frame", creating it if
it does not already exist.
