A fish tape (also called a draw wire, draw tape, or an electricians snake) is a tool used by

electrician An electrician is a tradesman, tradesperson specializing in electrical wiring of buildings, transmission lines, stationary machines, and related equipment. Electricians may be employed in the installation of new electrical components or the ...

s to route new wiring through walls and

electrical conduit An electrical conduit is a tube used to protect and route electrical wiring in a building or structure. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Most conduit is rigid, but flexible conduit is used for some purp ...

. Made of a narrow band of spring steel, by careful manipulation, the tape can be guided through confined spaces such as wall cavities or conduits in many countries. The goal is to push toward an area where guide string has been dropped inside the confined space and to pull it through, so the guide string can then be used to pull through various types of wiring, such as phone wire, network cables or speaker wire. Fish tape is designed to pull through guide string only. Using it to directly pull the target wire can damage or warp the fish tape.

Design

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.

Thermal insulation Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with s ...

, firestops, pipes, HVAC ducts,

s, and other obstructions make use of a fish tape more challenging. The "tape" can be made from many different materials including

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

fiberglass Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...

, and

nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...

. The tape usually has a special end ranging from a hook or loop to a specialized fastener device to allow the user to attach the tape to the guide string (or a very light cable) before pulling.

Invention and patent

Keith Leroy Wilson of Colorado Springs, Colorado, owner of the Electrical Construction Co, founded in 1947; invented the Fish Tape Snagger. Wilson filed the original patent on 29 Mar 1960 and Patent # 3,035,817 was awarded on 22 May 1962 by the US Patent Office.

Double use

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 sometimes attach a battery and a

doorbell A doorbell is a signaling device typically placed near a door to a building's entrance. When a visitor presses a button (control), button, the bell rings inside the building, alerting the occupant to the presence of the visitor. Although the ...

buzzer A buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical, or piezoelectric (''piezo'' for short). Typical uses of buzzers and beepers include alarm devices, timers, train and confirmation of user input such ...

to two fish tapes so that when the ends of the tapes make contact with each other (within the wall), the bell rings.

References

{{Hand tools Mechanical hand tools