In a single wire with a single point attachment configuration, what is the term used for the wire that supports the signal head?

In a single wire with a single point attachment configuration, the term that refers to the wire supporting the signal head is "messenger wire." This type of wire is specifically designed to bear the load of the signal head and keep it securely positioned, ensuring that it remains stable and properly oriented for visibility. Messenger wires are integral in providing the necessary tension and support for signal installations, allowing for effective placement in various environments.

The other terms listed do not accurately describe this function; for example, support wire suggests a different kind of structural role, while guide wire implies directional assistance rather than load-bearing. Signal wire is typically related to the electrical connections rather than structural support. Thus, "messenger wire" is the most precise term in this context.