Extension cords with outlet boxes are lengths of flexible electrical cable used to provide portable outlets to devices located far from a power source. They have a two- or three-prong plug at one end that connects to a power source and one or more metal outlet boxes with receptacles at the other end that devices plug into. In general, the more power needed by a device, the thicker the extension cord (or lower the gauge) needs to be to support the electrical current flowing through the cord. These cords are commonly used in commercial and industrial applications when a device's cord is too short to reach a power source or where outlets may be scarce.