Fenders are to be selected taking into account two quite distinct functions they have to fulfill: - During berthing manoeuvres fenders have to avoid damage to the ship and to the berthing structure; - After ships are already berthed and moored, fenders have to keep them quiet during loading and unloading operations. To fulfill the first function fenders have to be able, while deflecing, to absorb a very large amount of energy. To fulfill the second function fenders need to be able, while recovering their form, to dissipate a large amount of energy. Besides, they have to contribute to reduce or to increase the natural period of oscillation of already moored ships, depending on their tendency to oscillate in phase or out of phase with waves reaching the berths.