Like their smaller 10-32 counterparts, they can be used in tapped rails as well as cage nuts. The 12 is the drill size, and the 24 refers to the number of threads per inch.
Every screw has a Pilot Point, which is a smaller section of the un-threaded screw that guides the screw into the tapped hole or cage nut. This minimizes the risk of cross-threading and damaging the screw or the receptacle.
The screw itself has a black oxide coating and is constructed from cold hardened steel, making it perfect for all of your needs.