The official name is “bolt-rope” and some refer to it as the “bead”.
It is located along the top edge of the canopy roof and fed into the “C” track along the roof line of the trailer.
On a standard setup, the bolt-rope is sewn to the canopy.
For ease of installation, it can be made as a separate piece that zips to the main body of the roof. (See Zippered Bolt-Rope Strip.)