Found it. E is for Mandatory Excusal for the following...
The following faults call for mandatory excusal. The
scribe sheet shall be marked “E” and the dog and handler
are excused from the ring.
1. Excessive handling, harsh commands, or corrections.
2. Unsportsmanlike conduct.
3. A dog that leaves the course area and discontinues
working.
4. A dog that discontinues working the course and
is unresponsive or out of control.
5. Exceeding the maximum course time.
6. Dogs fouling (includes vomiting) the ring at
any time.
7. Four Paw Rule. If a dog commits all four feet on
any portion of a contact obstacle and fails to negotiate
that obstacle, the judge shall instruct the
handler to move the dog on to the next obstacle.
If the handler re-attempts the obstacle, the dog
shall be excused.
8. Inappropriate collar on dog discovered after the
dog has started its run.
9. A handler that runs the course with handling
aids.
10. Training in the ring including corrections, purposefully
touching the dog in order to get it to
perform an obstacle or petting the dog on the
Pause Table or contact obstacles to reinforce a
behavior.
11. Dogs biting handler, beyond playful nipping.
12. Exceeding the fault limit of the class. Fault limits
may be applied only if both the judge and Trial
Chairman agree that it is in the best interest of
the trial to do so. If applied the fault limit shall be
either three (3) or four (4) separate faults that
would normally result in a score of less than 85.