Gaffer's tape is a flexible, strong, fabric-backed adhesive tape that comes in lengths ranging from one inch (2.5 centimeters) to a potential of six feet (1.8 meters), with the most common width being four inches (approximately 10 centimeters). Gaffer's tape is similar to duct tape, but it is more flexible, it can be molded over a variety of shapes, and it usually leaves no residue. Gaffer's tape most commonly comes in a matte black finish designed for use on stages, but it is manufactured in a range of colors for various applications, including red and bumblebee-striped to indicate hazards.

Gaffer's tape can easily be torn along any side, although it will not break if pulled or twisted. This makes it ideal for applications in which a wide variety of tape lengths and widths are needed, because users do not need to carry scissors to cut the tape. Gaffer's tape is widely used in the film and stage industries, and the common name for the tape probably comes from the head of the lighting department for a film crew, who is also called a gaffer. A company called Gaffa also manufactures Gaffas Tape, so both spellings are accepted. Gaffer's tape is manufactured in large rolls that are six feet (1.8 meters) across and cut down to the size needed, making it theoretically possible to custom order a roll of tape in that size, although it might be challenging to unroll and handle.

Gaffer's tape is capable of adhering to a wide variety of surfaces, although it sometimes removes paint or finish from wooden surfaces. The tape can be easily removed or repositioned with gentle traction. Gaffer's tape is also somewhat heat and water resistant and capable of handling low temperatures, which is why it is used in many stage applications, such as taping down trailing cables and cords for safety; placing blocking marks for furniture, actors, or cameras; and taping set pieces together. Gaffer's tape is also commonly used to label and seal film cans, as well as to label channels on light and sound boards. Costume departments have also been known to use gaffer's tape for emergency alterations.

Most members of electrical and sound crews on films carry rolls of gaffer's tape in various sizes and colors, and the multipurpose, sturdy tape has spread to other industries as well. Librarians, for example, frequently employ it on the binding of damaged books, and the military uses gaffer's tape in a number of environments as well.