Elven Rope was a special kind of rope made by the Elves.
In the book, Sam simply takes a coil of Elven Rope from the three coils put in the bottom of each boat. Made of Hithlain, the ropes are light weight, grey, strong, and silky to touch. When Frodo slips while climbing down a cliff-side and temporarily loses his sight, the rope, gleaming faintly, was the first thing he saw. After both Frodo and Sam have made it safely to the bottom, the rope comes down when Sam calls it.
Portrayal in adaptations
The Lord of the Rings film trilogy
Later on in the movie, The Two Towers, Frodo and Sam capture and bind Gollum with it after being attacked by him in Emyn Muil. He complains that it "burns and freezes" him and demands that it be taken off of him. The rope burns Gollum in the book due to his dark tainted soul and body.
- LOTR: The Two Towers, book 4, chapter 1, page 241 " 'Have it your own way, Mr. Frodo,' [Sam] said at last, 'but I think the rope came off itself -when I called.'"