Tautliner or curtainsider is a type of semi-trailer used in trucking and transportation. It is characterized by its flexible, curtain-like walls that can be rolled up or down to allow for easy loading and unloading of cargo. These walls are made of a strong, waterproof material that helps to protect the cargo from the elements and keep it secure during transport. Curtain trailers are often used to transport large, bulky items such as furniture, appliances, and construction materials, and are typically pulled by a tractor trailer. Some curtain trailers have a side curtain that can be opened for loading and unloading, and some have a rear curtain that can be opened for loading and unloading.