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How to prevent electrical accidents with hand tools
Never use any electrical hand tool that does not carry the underwriters laboratories seal of approval.
This seal indicates the tool has undergone extensive testing and has been found to be safe when properly maintained.
Older tools with a two-wire design should be immediately upgraded to a three-wire system by qualified personnel.
If your tool cannot be upgraded, discard it. Most power tools in use today have a three-wire system.