The first step is to determine the method to be used to mount the Tripp Lite PDU in a rack: either vertically or horizontally. When mounted vertically, it occupies no rack spaces (0U), because it is attached onto or behind one of a rack's vertical rails. Select PDU models feature button and tab mounting to simplify horizontal (0U) installation. Users simply slide mounting buttons (located on the PDU) into mounting tab holes (featured on most major racks). Mounting takes only a few seconds, much easier than the standard method of mounting the PDU with screws. When mounted horizontally, the PDUs commonly occupy one or two rack spaces (1U or 2U). Since PDUs generally function as the entry point for power into a rack, most offer a 10- to 15-foot input cord. With long input cords, PDUs can be mounted anywhere within a rackmount enclosure, even at the top of a rack, and still be plugged into a distant power source. Depending on the model, PDUs can also be mounted on a wall or under a counter.