A gaffer, sometimes called the chief lighting technician, is in charge of all of the electrical and lighting requirements on a film set or theater stage. The gaffer directs electricians and other workers on the set to place all of the lighting equipment. The cords and cables are secured in place with gaffer's tape.
Gaffer's tape is a very strong cloth tape that is waterproof and will withstand low temperature without losing its grip. For a strong tape, however, gaffer's tape is easy to tear by hand, which makes it easy to apply because no special cutting tools or dispensers are required.
Gaffer's tape also comes in different widths and thicknesses. One type is called "spike tape," which is easier to tear than regular gaffer's tape because it is thinner. Its thinness allows it to be put on a stage floor and be invisible to the audience. Gaffer tapes are commonly available in weights from 8 mils to 11 mils.
Perhaps gaffer's tape's biggest claim to fame is its ability to be removed without leaving a sticky residue behind or pulling paint off of walls. Gaffer's tape uses a synthetic rubber adhesive that removes cleanly.
Gaffer's tape comes in a variety of colors, not just black, which is usually non-reflective. Because gaffer's tape is often used by directors to mark the spots where actors should stand, different colors of tape can be used for different actors, so it makes stage direction a bit easier.