A curtain side is a truck with cloth sides allowing for easy loading/unloading. Essentially, it is just a flatbed truck featuring an upper structure connected to it, used as a tarping system. There are two main types of curtain sides: the Conestoga and the Tautliner.
The Conestoga uses a tarp sliding system. When the tarp is pulled forward, it exposes the flatbed almost completely, giving access to load cargo onto it from the sides, back and overhead. The structure of this type of curtain side makes the trailer up to 107 inches wide, with a load capacity of 102 inches. This creates somewhat of a disadvantage if your cargo is at 102 inches wide, and it moves or shifts during transit, the system cannot be open or closed. Placement of cargo inside of the curtain side is important for it to function properly.
The Tautliner curtain side is a flatbed trailer that features doors located on the front, back and roof. There are curtains on each side of the trailer, that slide back and forth, like a regular household window curtain works. Because of its framework, this type of curtain side does not have the ability to open up for overhead loading. However, the tautliner has a wider cargo capacity, exceeding the 102 inches that the Conestoga can handle. It is also a more flexible model, so there is room for items inside of the truck to move around a little.
Curtain sides are most commonly used by suppliers of building material. The convenience of being able to slide the tarp makes it easy to load large amounts of supplies right onto the flatbed. The tarp system can be easily moved to open up access to the flatbed, for quick loading and unloading, which is why many companies that produce large, bulky items prefer to use a curtain side when it comes to transporting material.