Symbolism of night
Night is typically associated with the obscurity and mystery of darkness, with the Moon as its singular eye. It is the symbol of ignorance, the unconscious, and latent potential, and is represented by the goddess Nyx, who is the mother of sleep, dreams, sexual pleasure, and death.
Symbolism of nail
The nail is most often assosciated in the Christian tradition with the crucifixion of Christ, and thus symbolize his passion. The nail also represents the Cosmic Axis, or Axis Mundi, around which the heavens rotate. The image has also given rise to such expressions as, "to hit the nail on the head," which means that the thinker has precisely analyzed the issue.
