Frank shot his arrow. It streaked upward, carrying its glittering rope.
When it reached the top, the metal point fractured into a dozen lines that lashed out and wrapped around anything they could find—parts of the wall, a scorpion, a broken water cannon, and a couple of defending campers, who yelped and found themselves slammed against the battlements as anchors. From the main rope, handholds extended at two-foot intervals, making a ladder.
“Go!” Frank said.
Percy grinned. “You first, Frank. This is your party.”

The Son of Neptune, Chapter XI