Grass is vulnerable at the crown (the bulb-like structure at the soil level). If unprotected, the crown of the grass can be easily damaged by over-playing, as well as using sand as a top dressing that can be abrasive.
reRubber has a specially sized crumb rubber that protects the crown, by cushioning the impact before damage occurs. Simply broadcast the crumb rubber as you would disperse sand. Because the rubber comes from a tire, it will not breakdown nor affect the grass.