<P> Knob - and - tube wiring ( sometimes abbreviated K&T ) is an early standardized method of electrical wiring in buildings , in common use in North America from about 1880 to the 1930s . It consisted of single - insulated copper conductors run within wall or ceiling cavities , passing through joist and stud drill - holes via protective porcelain insulating tubes , and supported along their length on nailed - down porcelain knob insulators . Where conductors entered a wiring device such as a lamp or switch , or were pulled into a wall , they were protected by flexible cloth insulating sleeving called loom . The first insulation was asphalt - saturated cotton cloth , then rubber became common . Wire splices in such installations were twisted together for good mechanical strength , then soldered and wrapped with rubber insulating tape and friction tape ( asphalt saturated cloth ) , or made inside metal junction boxes . </P>
<P> Knob - and - tube wiring ( sometimes abbreviated K&T ) is an early standardized method of electrical wiring in buildings , in common use in North America from about 1880 to the 1930s . It consisted of single - insulated copper conductors run within wall or ceiling cavities , passing through joist and stud drill - holes via protective porcelain insulating tubes , and supported along their length on nailed - down porcelain knob insulators . Where conductors entered a wiring device such as a lamp or switch , or were pulled into a wall , they were protected by flexible cloth insulating sleeving called loom . The first insulation was asphalt - saturated cotton cloth , then rubber became common . Wire splices in such installations were twisted together for good mechanical strength , then soldered and wrapped with rubber insulating tape and friction tape ( asphalt saturated cloth ) , or made inside metal junction boxes . </P>
when did builders stop using knob and tube
when did builders stop using knob and tube
1930s
1930s