All in all there are 360 different angles the
eyepiece mount can be shifted along. There are 90 degrees at which it can be
tilted in 360 different directions. Getting the eypiece mount "true" is the
first task in collimating a telescope.
The Flat comes next. It is likely positioned
correctly within the range of the eyepiece mount's shifting movement. However
it may need to be CENTERED correctly
in the telescope's tube, or may need to have its beam reflecting ANGLE adjusted.