Clark Griswold loves his Christmas lights in the movie, National Lampoon's Christmas Vacation. The humorous collection of extension cords layered into each other in a single garage socket, while funny in the movie, in real life, presents safety concerns for your family and home. 

Knob and tube wiring was an early form of electrical wiring in buildings common in North America from about 1880 to the 1930s. Knob and tube gets its name from the ceramic tubes used to pass the wiring through beams and the ceramic knobs used to anchor the wiring in place. The wire was a single piece of copper wrapped in an asphalt dipped cotton wrap. There are several disadvantages and dangers to knob and tube wiring. Primarily a house with knob and tube wiring will not have grounded outlets and any grounded devices (three prong) will not be able to be plugged in. In addition this wiring often poses a fire hazard. Most insurance companies will request that you evaluate having this wiring replaced.