Features

• Designed to remove the oxide layer from aluminum conductors prior to jointing
• For turning down material.
• Shaping wood or other material. Typically a hand tool, it consists of a generally tapered rectangular, round, or half-round sectioned bar of case-hardened steel with distinct, individually cut teeth. A narrow, pointed tang is common at one end, to which a handle may be fitted

Here's more about it:

• File: The file itself consists of a hardened steel bar with a rough surface, used for filing, shaping, or smoothing materials by removing small amounts of material through friction.
• Insulation: The handle or sometimes the entire file may be coated with insulating material, such as plastic or rubber, to provide protection against electrical shocks. This insulation ensures the user remains safe while working in areas where accidental contact with live electrical conductors could occur.
• Application: Insulated files are commonly used by electricians, linemen, and technicians who work in environments where there is a risk of electrical exposure, such as maintenance of electrical systems, electronics assembly, or electrical repairs. The insulation helps reduce the risk of shock while still allowing for precise work.
  
  

These files are part of the essential safety tools for professionals who need both precision and protection in their work environments.