For overhead conductor spans, what shall not be used for support other than temporary holiday wiring?

In the context of overhead conductor spans, vegetation should not be used for support, except for temporary holiday wiring. This is because tree branches and other forms of vegetation can pose significant safety risks as they can sway or move in the wind, potentially causing the conductors to become loose or to sag dangerously low. Additionally, as vegetation grows or is affected by weather conditions, it may interfere with the stability and integrity of the wire supports, leading to potential hazards like electrical shorts or outages.

Using proper support structures like metal poles or suitable types of insulation ensures the safety and reliability of electrical overhead installations. These materials provide a stable, long-term solution that can withstand environmental forces without degrading over time, unlike vegetation, which is inconsistent and unpredictable in its behavior.