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A knob is used in knob and tube wiring to allow the wires to be strung along a wall or ceiling.

There are two basic kinds of knobs, clamp knobs and wrap knobs. The first three pictures show clamp knobs, where the knob is made in two pieces with one or two channels in the top and bottom for one or two wires to fit in. The knob has a central nail that anchors the knob to the the wall or ceiling sandwiching the wires between the two pieces of the knob. Clamp knobs come in glazed and unglazed (shiny or not shiny).

The fourth picture shows wrap knobs, where the wire is not sandwiched between two pieces of the knob but tied around the channel in the one-piece knob. These were often used in conjunction with clamp knobs where the wire had to turn a corner but were also used for running the wires in straight lines. We have never encountered unglazed wrap knobs. The wrap knobs come in different sizes, as you can see in the picture.

We have a full description of knob and tube wiring and Wikipedia's knob and tube wiring page has great pictures of knob and tube installations.



Knobs classified as good may have slight chips, a little dirt, slightly bent nails.


Knobs in fair condition are still functional, but may have larger chips but no major breakage, and can have significant dirt, marks, and/or discoloration.

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