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I have plaster and lath walls in my house. The house is wired with knob and tube so I'm looking to upgrade. In order to pull my new wires through the walls and hit my electrical box I will have to remove the box itself, correct? Since I wouldnt be able to accurately guide my fish tape into the small opening in the box.

If I do have to remove the box how do I do that? I noticed that there were these two tabs on the right side of the box that look like they are holding it in place.

Another thing I was thinking about was using the pre-existing wire as a pole station but I'm not sure if I'll be able to do this because of the porcelain knobs connecting it to the studs. I'm not sure if there is any knob in the wall itself Or if it’s just free and can be used to pull new wire. One of the wires seemed pretty loose when I gave it a tug.( Like it wasn't connected to anything in the wall) * I only pulled it out about a foot or so*

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  • sounds like a job for qualified electrician
    – Traveler
    Commented Oct 27, 2022 at 1:44
  • Pictures would help and there are knobs in walls.
    – JACK
    Commented Oct 27, 2022 at 12:58

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Be very aware that knob & tube wiring is ancient at this time. Any messing with it has a high likelihood of cracking the insulation leaving the wire unsuitable for continued use. Depending on your jurisdiction, you may be required to replace it all once you start messing with it at all.

You are correct in your assessment that you will need to pull boxes out of the wall in order to fish new cables into them.

I'm not sure what the "two tabs on the right side of the box that look like they are holding it in place" without a picture, but it's possible that what you're seeing is the folded part of a "battleship" that is often used to hold a metal box into an existing wall when it's used as old-work (when the box cannot be directly attached to a stud). If these are battleships, then you would have to unfold them to release the box. I'd imagine that you would probably have to replace them with new ones. If nothing else, there's a decidedly non-zero chance that it might drop down into the wall as you're attempting to remove it, so you may as well have some on hand just in case.

The old-work boxes might also be held in via plaster ears, or they may be new work boxes that are nailed into studs. You'll have to investigate each box to determine how it was attached to the wall so you can remove it.

If you have actual knob and tube wiring, you won't be able to use it to fish new cable through the wall. The wires are actually clamped down within the knobs and they'll prevent it from moving very far. You may have grabbed hold of one where there was some slack, but you will, most likely, quickly run out of that slack.

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    I'd recommend emphasizing the dangers of messing with k&t upfront in the answer. Some jurisdictions allow k&t to stay in place until you touch it and then it must all be replaced. Others likely allow partial retrofits, or attaching to k&t in add-on construction only. Either way, handle k&t with care. Commented Oct 27, 2022 at 19:22
  • Good point, @FredricShope. Done.
    – FreeMan
    Commented Oct 27, 2022 at 19:30

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