Please choose the correct ending to complete the given sentence: Home and Garden: [header] How to prevent electrical accidents with hand tools [title] Never use any electrical hand tool that does not carry the underwriters laboratories seal of approval. [substeps] This seal indicates the tool has undergone extensive testing and has been found to be safe when properly maintained. [title] Older tools with a two-wire design should be immediately upgraded to a three-wire system by qualified personnel.

Ending1: [substeps] If your tool cannot be upgraded, discard it. Most power tools in use today have a three-wire system. Ending2: [title] Older tools with a three-wire design should be immediately upgraded to a three-wire system by qualified personnel. [title] Newer tools with a four-wire design should be immediately updated to a six-wire system by qualified personnel. Ending3: [step] The basic system systems' systems should be shot down, primed, and kept solid. A professional process for calipers is also helpful if the machine has not been properly primed and supported by the workers. Ending4: [step] However, you can sometimes lower your capability by changing the scanner settings and other functions as needed. [title] Having knowledgeable technicians unmodified is an important part of maintaining safe hand tools.

Answer format: ending1/ending2/ending3/ending4