Hold the nail so that it looks like he is straight.
Then turn it slowly.
EFFECT: The mentalist has a straight nail. The nail bends visually for the spectators eyes.
THE SECRET: First you bend a nail. For the greatest effect a big nail.
PRESENTATION: Stand before the spectator so that the light comes from behind you. Hold the nail so that the spectator see the silhouet of the nail and it looks like it is straight. Then turn it slowly so it's like it bends.