1) Place a folded playing card in a glass.
2) Fill the glass with rice... Don't let anybody see steps 1& 2.
3) Have a card selected and signed.
4) M*rc*ry F*ld the selected card after making it vanish.
5) Shake the glass with your empty hand and watch the card rise.
6) Appear to remove the card but secretly push the 'duplicate' card back in as you simultaneously appear to remove it by releasing the signed M*rc*ry F*ld C*rd.
7) Make sure you cover the duplicate card with rice so it is no longer seen.
Figure that bit yourself!