The planning of the margins ought not to be considered
a difficult job.  In fact, if you will simply think through
this procedure step by step, you will realize that figuring
margin stops is quite easy.  The formula for any particular
line length is the same as for any other.  When you compute
your left and right margins, you are engaged in a short-cut
form of horizontal centering.  As with horizontal centering
the first thing you must know when you plan margins is your
center point.  Using standard sized paper, the center point
is fifty on elite machines and forty two for pica machines.
     Once the line length has been determined, it must then
be divided in half; this is because one half of the line of
type must go to the left of the center point, with one half
going to the right of center.  Let's assume you are using a
sixty space line.  The first thing you must do is to divide
sixty by two, the result being thirty.  To compute the left
margin you subtract thirty from the center point.  Assuming
a pica typewriter, you would subtract thirty from forty two
to obtain a left margin of twelve.  The right margin is the
sum of the center point and thirty--plus five extra spaces.