Knob-and-Tube Wiring

The earliest wiring system was called knob-and-tube wiring, and you’ll still find this in houses built prior to the early 1950s. This was an inherently safe system in which the hot wire and the neutral wire ran separate from each other through walls, floors, and ceilings. Each wire was covered with cloth insulation and ran through ceramic tubes when passing through floor joist and wall studs or into electrical boxes at lights, switches, and receptacles. The wires were secured to ceramic knobs when they ran along a joist or stud.

Electricians were a little anxious about this new electricity stuff, so most original knob-and-tube work is very neatly done. Wires were twisted together, soldered with lead, and then taped to make secure connections. The main problem with knob-and tube wiring is what happens in the intervening years when homeowners and amateur electricians hack into it