Abswer: Gear for rough, uneven surfaces or terrain is adapted towards protection than other designs. Every obstacle that you will encounter as you run on trails are threatening and different such that they can put you out of commission for weeks in case of an injury. Rock plates are therefore essential in trail running shoes to forestall such an occurrence. They are solid pieces of material embedded in the sole of most trail running shoes and help to shore up its rigidity if you happen to step on a rock as you run. If the sole of your running shoe is too flexible, there is no way you can avoid incurring debilitating injuries or pain. But this unfortunate occurrence is what a rock plate is designed to prevent.