Used in its vertical format, this dolly is great. Its lightweight, manueverable, and can handle 3 or 4 archival boxes with ease. When laid out horizontally, however, its drawback is clear: the removable upper handle does not attach securely to the 4-wheeled base. The only thing keeping the u-shaped handle attached to the 4-wheeled base is one lone thin pin that secures only one side of the u. As you manuever around, & especially on turns, the handle threatens to come loose from the base. Undoubtably, repeated usage in this format will wear down the lone pin. Ideal solution would be to secure the handle with 2 pins instead of 1. Even then, the pins are so thin I would take the listed "600lb capacity, horizontal" with a grain of salt.