In any reinforcement detailing there are two sizes of bars used in the slab. These are the main reinforcement bars and distribution bars? If there is any load on a slab the bottom of the slab undergoes positive moments (Sagging) and the supports undergo negative moments (Hogging). The bottom part together with the top part of the slab will undergo extreme tension simultaneously. In this video, we will discuss the difference between the main bar and the distribution bar.