Just wondering what Tube And Knob wiring is. My house was constructed in 1952.

Knob and tube wiring - Wikipedia, the free encyclopedia

Ceramic tubes to route knob and tube electrical wires through building framing members:

Wherever the knob and tube circuit wires pass through building framing lumber a ceramic tube is used to insulate the wire from the wood.

These thick ceramic tubes are a good insulator separating electrical wire from wood - if both are un-damaged.

Ceramic knobs to support knob and tube electrical wires passing over building framing surfaces: Where the knob and tube wiring is surface mounted in a building it is attached using a ceramic "knob".

These ceramic knobs are a good insulator provided they have not been damaged or modified.