The hazard
A live wire looks exactly like a dead one, and your body can become part of the circuit. Electrical contact can cause shock, burns and electrocution, and even a small shock can make you fall from a ladder. How badly you are hurt depends on how much current flows, the path it takes through your body and how long the contact lasts.
The action
OSHA's general industry rule requires a visual check of extension cords and corded tools before use on any shift, and it is a good habit on every job. Look for cuts or cracks in the jacket, missing or bent prongs, loose plugs and crushed spots. If you find damage, stop, take the item out of service, tag it and tell your supervisor. Never tape over a damaged cord or cut off the ground pin to make a plug fit. (29 CFR 1910.334(a)(2)(i))
ASK THE CREW
Where are the overhead lines near our work, and what equipment or materials could reach them?
From the talk: Electrical safety. Read it in full, free, with the questions and the sign-in sheet.