The heat tape has a conductive bus (wire) running down each side. If you notice, the cable that plugs to the wall is hooked to each side of the heat tape with clips. One side is positive, the other is negative. They cannot touch because that would cause an electrical short which is the cause of fires - that would be like shorting your extension cord by stripping off the insulation that separates both wires that make up the cord. Make sense?