Bolt-rope
A typical "back drop to trailer" is a fabric panel used on "rise above" canopies. This vertical panel closes off the gap between the elevated top of the canopy frame and the trailer roof. A zippered connector for the back drop is standard on a Larsen "rise above" style canopy. Another method of filling this...
Bally Curtains is a term sometimes used in the industry for Half Height Skirts. Please see "Half Height Skirts"