The Pro-Porta Trailer from Pro-Tainer allows users to carry multiple units that stay securely on the trailer. It has a solid floor, ramps for loading and unloading, and durable paint. Removable dividers allow hauling of standard-sized units, as well as handicap-accessible units. Various capacities are available. Each unit will firmly stay in place. 800-248-7761; www.protainer.com.