I am mounting a mirror in my hallway. I have plaster/lath walls and am planning on drilling a hole to insert a toggle bolt to hang the mirror on.

I marked the location and was ready to drill when I decided to use a non-contact voltage meter to see if any wires were in the area. It turns out there is wire going from a switch to an overhead light right though the area I'd like to drill my hole.

Obviously the first step is to flip the breaker, but I am not sure how I will know if I am damaging the wiring when I drill my hole. How do I drill the hole while knowing I'm maintaining the integrity of my electrical system?

1 Answer 1


Use the depth of the plaster/lath; say it's 5/8".

  1. Put a piece of tape around the drill bit at 5/8" to ensure you don't drill deeper.
  2. Drill the surface hole 5/8" deep.
  3. Once the surface hole is made, you can turn on the electricity and insert a non-contact inductive wire sniffer (like this one from Fluke: https://www.amazon.com/Meterk-Non-Contact-12V-1000V-Flashlight-Multi-sensor/dp/B0711KGPYD).

Note this will only detect the "hot" line (not ground).

  • 3
    Or, 3. Stick your finger in the hole and see if anything's there.
    – isherwood
    Jan 2, 2018 at 19:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.