Why Use It? Also known as a “single-drop” trailer, the step deck flatbed has a lowered deck. This allows the step deck to haul loads that are too tall to be transported with a conventional flatbed trailer and still require a 30 to 42 foot bed length. For example, a 48 ft step deck trailer can haul construction machinery, industrial machinery, oversized vehicles, modular buildings and other cargo that needs extra height clearance.