In the newest version of the mod for 1.6.2, ropes don't exist anymore. They've been replaced with the Lead, an item from Vanilla Minecraft.
Rope was created by putting five pieces of String in an X shape. It was used to lead around tamed Mobs.
*Note*: The Ropes Can NOT attach to Fences like the Leads can!
Rope were used to pick up Kitties by their feet, though the Kitties got extremely annoyed if you carried them this way and sometimes attacked you once released.