Short post on a trick my electrician taught me about fishing wires when you have access to the floor beneath:

  • Take a length of thin spring steel wire (called music wire in some circles), 18-24 inches long.
  • Grind a point into the end.
  • Chuck the other end into your drill.
  • At the base of the floor where you want to put the output, start “drilling” with the wire. While it does not have much of a cutting surface, it will only take a minute or two to go through the floor and subfloor.
  • Go below and find where the wire poked through. Now you know exactly where to drill upwards through the subfloor into the wall. Of course, you have to offset to get into the wall cavity, since the wire represents a spot outside of the wall.
  • Once you’re done, you can just reverse the wire out. The hole left is extremely small, and is generally invisible even for wooden flooring.