Wiktionary
tautliner
n. A curtain-sided truck or trailer.
Wikipedia
Tautliner
Tautliner or curtainsider is used as a generic name for curtain sided trucks/ trailers. It is the trade name of commercial vehicles built by Boalloy of Congleton, Cheshire, England. The curtains contain load retaining straps which, when released, allow the curtain to be pulled back and a forklift to be used for easy and efficient loading and unloading.
The company patented the concept in 1969, and credits much of its popularity to its adoption by the haulier Eddie Stobart.