Fish tape
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A fish tape is a tool used by electricians to route new wiring through walls. Made of a narrow band of spring steel, by careful manipulation, the tape can be "fished" (guided) through the confined spaces within wall cavities. Once guided through, the new wiring can be pulled into the wall by attaching it to the end of the fish tape and pulling the tape back from whence it came.
Fish tapes are usually stored coiled on a plastic reel. Because of this, they have a natural curvature and it is this curvature that allows them to be guided. By manipulating the reel, the end of the tape can be directed slightly. The tape is rigid enough that it can then be pushed in the direction in which it is pointing. In this way it can be easily guided through an empty wall cavity.
If the wall cavity is filled with thermal insulation, guidance of the tape becomes more difficult but usually not impossible . (For foamed-in-place insulation, it may actually be impossible.) The tape can often be guided between the wall panel and the vapor barrier or, sometimes, simply shoved through the bulk of the insulation.
Occasionally, two fish tapes are used from opposite ends of the wall. Because they each have a hooked end, one fish tape is capable of catching the other, and the one tape can then be pulled back, carrying the second tape out with it. Electricians have been known to go so far as hooking up a battery and a doorbell or buzzer to their two fish tapes so that when the ends of the two tapes make contact within the wall, the bell rings; this can greatly aid the "catching" of the second fish tape.
Also known as a draw wire or draw tape
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Tips for using:
- Two people can very helpful for this type of job.
- Running wire in one go, making the smallest securest bundle possible (double the strongest wire through the 'fishhead', using pilers to flatten the wire as much as possible and tape 2 inches up and down the fish tape and wire+wire bundle).
- Taping the length of the wire every foot or two helps to keep the tension tight and avoid snags.
- Use lots of lube (apply right below tape so it spreads before getting to the next tape).
- If fish tape gets stuck: wiggling, push-back-and-pull, or flipping it over and back (180 degrees one way, then back) can all help free it.
- Every bend doubles the resistance.
