What is one characteristic necessary for live line tools?

The characteristic of good insulation is crucial for live line tools because these instruments are used in high-voltage environments where workers may be exposed to live electrical components. Insulation prevents electrical current from passing through the tool to the user, ensuring safety while performing maintenance or repairs on power lines. This feature helps to protect the worker from electric shock, which can be fatal.

Other characteristics, such as thermal conductivity or magnetic properties, may not be relevant or necessary for the primary purpose of these tools, which is to safely handle electrical work. A heavyweight structure could also be disadvantageous, as live line tools are often designed to be lightweight for ease of use and maneuverability during operations. Therefore, good insulation stands out as the most essential feature for ensuring both safety and functionality in live line tools.