Security Thread
Hold the bill up to the light
and look for the security
thread, or plastic strip, that
is embedded in the paper
and runs vertically up one
side of the note. If you
look closely, the words
"USA TWENTY" and a
small flag are visible along
the thread from both sides
of the note.
This thread glows green
when held under an
ultraviolet light.
Watermark
Hold the bill up to the light
and look for the watermark,
or faint image, similar to the
portrait on the face of the
note. The watermark is part
of the paper itself and can
be seen from both sides of
the note.
Color-shifting Ink
Look at the number "20" in
the lower right corner on
the face of the note. When
you tilt the note up and
down the color-shifting ink
changes color from copper
to green and back again.
