Nails are miniature metal rods that have been ground to a point. By applying force to the nails, their points focus all potential energy into a small space, making it capable of being driven into hard substances. This makes for a potentially deadly projectile when propelled at high speeds.
The texture used for nail boxes, is actually scanned from a modern box of nails. While the texture for nail boxes is low resolution, the name of the real-life tool company, Paslode, can be made out in the upper right corner.