Now select the Rectangular
Marquee Tool and make a selection similar to Ex. 2. This
is a lot easier if you zoom in to about 300%.
Ex. 2
Now fill the selection
with 60% black (Edit - Fill). Keep your selection and
use your arrow keys to move the selection 2 pixels down.
(Hit the "down arrow" 2 times). Fill the selection with
100% white. Now move your selection up 2 pixels an fill
the selection with 60% black. Deselect and your
finished!