See the little bushings on the inside of the cut out of the rocker. Those bushings ride on the bearing race on the outside and on the chassis on the inside. The bolt then goes through the assembly and bolts the bearing race solidly to the chassis. That way when the rocker pivots, it pivots on the bearing and NOT on the bolt. Pivoting on a bolt is very, very bad as the bolt will eventually wear out and then you will get to go for a fun ride as your suspension falls off.
