A type of electrical wiring that was commonly used in homes built before the mid-20th century. The system consists of ceramic knobs and tubes that are used to support and protect the wiring as it runs through the walls and ceilings of a building. In this system, the hot and neutral wires are run separately and are not enclosed in conduit or other protective coverings. While knob-and-tube wiring is still considered safe for use, it can pose a fire hazard if it is not properly maintained or if it is not upgraded to meet modern safety standards. Additionally, it does not support the amount of electricity a modern home requires, making it difficult to add new appliances and electronic devices to a home with this type of wiring. Due to this many insurance companies do not provide coverage for properties with knob-and-tube wiring.