For nailguns and supernailguns. A small box holds 25.

Quake 1 Manual

In Quake, Nails (also called Flechettes) come in two pickups: small and large. Small boxes hold 25 nails, while large boxes hold 50 nails. They supply both the Nailgun and the Super Nailgun. The boxes have NIN (Nine Inch Nails) written on the side, a dedication to Trent Reznor for creating the game's soundtrack. Though originally created as a joke, Trent Reznor's approval of the design convinced id Software to leave it in the game.

If a Nail does not make contact with anything within seven seconds, it will disappear.