Z Scale 2 Bay Covered Hoppers. Covered hoppers handle a variety of loads and are a common site on any railroad. Covered hoppers are designed for carrying dry bulk loads, varying from grain to products such as sand and clay. The cover protects the loads from the weather. Similar to an open hopper car, covered hoppers tend to contain 2, 3 or 4 separated bays. Each of these can be loaded and emptied individually, with access at the top to load the materials and visible chutes at the bottom for unloading.