What's the texture like? Is it smooth, ribbed, velcro, or what? Stiff or flexible? How long is it? It could be a random bit of cable wrapping, or packaging material, or adhesive tape.
Is the trailer new? Sometimes, odd pieces leftover from manufacturing emerge from the corners during the first few weeks of traveling.
2012 Fun Finder X-139 "Boondock Style" (axle-flipped and extra insulation)
2013 Toyota Tacoma Off-Road (semi-beefy tires and components)