The rope is a loop of coiled vines at the storeroom left of the Living Quarters. Jump into the updraft from the steam vent and it will throw you to the roof.
The "rope" is a coil of old vine on the roof of the , left of the Living Quarters. You need it underground at the Hub.
it's on top of on of the buildings on the far left
its in the museum on mainstreet of steamworks island :)
In the underground below the Hub, you use it to rope a steam pipe to knock out an attacking monster in the pipes.
It's Steamworks Island #14th Island
(The solution is at the related question "How do you beat Steamworks Island")
the crab on steamworks island is next to the living quarters
You go to Steamworks and head to the museum and there is the Deogen
steamworks island
There is a video walkthrough at the related link below. There are written WikiAnswers solutions at the related questions, as there are for all Poptropica islands. (How do you beat Steamworks Island) (What is the walkthrough for Steamworks Island)
Steamworks island
you can get it on the far left of steamworks island, past the living headquarters.