Fairly easy to install, roof de-icing systems prevent ice damming in gutters by heating the gutter area (where ice dams form) and melting pathways whereby water can flow off of the roof.
Cables go along the gutter and are also arranged in a triangular pattern in the eaves above it. The end of the cable is plugged into a grounded, weatherproof outlet.
When installing de-icing cables, always follow the manufacurer's instructions - for maximum benefit and for safety. Most manufacturers have online video installation guides to help you out.
A couple of installation safety guidelines: