An overhead service wire runs from a distribution line or transformer to a weatherhead on the roof or side of a structure. The service wire may appear as a single wire or as three wires twisted together. A hollow steel tube called a service mast carries the service wires from the weatherhead to the meter.
A weatherhead is a waterproof hood that protects service wires as they enter a building. Other names for this apparatus include weather cap, service head or service entrance cap. One side of a weatherhead slopes down to allow moisture to flow away from the connection. It also contains watertight rubberized gaskets that protect the wires as they pass under the hood and into the service mast.
Overhead service wires should always be treated as energized and dangerous to contact. Like power lines, these wires are coated for protection against the elements and not for insulation against electric shock.