What is the term for the rope used to extend an extension ladder?

The correct term for the rope used to extend an extension ladder is "halyard." This term specifically refers to a rope or line used to raise or lower items, in this case, the sections of the extension ladder. Halyards are often used in various contexts, including sailing, where they are employed to manage sails. In the case of an extension ladder, the halyard plays a critical role in allowing the user to safely and efficiently extend and retract the ladder sections.

Other options may seem plausible but do not accurately describe the function of the rope for extending a ladder. "Rope Line" is a more generic term that does not specifically convey the purpose of extending a ladder. "Extension Cord" refers to an electrical cord used to provide power to devices, which is unrelated to ladder operation. Lastly, "Support Line" implies a line used for stabilization or support, not for the mechanism that extends the ladder. Therefore, "halyard" is the most precise term for the function it serves in this context.