Gaff tape also known as “Gaffers Tape” is a heavy cotton cloth pressure-sensitive tape with strong adhesive and tensile properties. (https://en.wikipedia.org/wiki/Gaffer_tape
In other words, gaff tape is like duct tape except for the fact that it is more resistant to heat and is easily removed off of surfaces without damaging the areas which was adhered.
Why should you use it? Well there are over 1000+ ways it can and should be used on set. For myself, It is important to have on set so you can tape down power cables to avoid tripping hazards. It is used to write on (label), hide, stand, wrap, tape, fix almost anything on set. Depending on your production, the Best boy and grip will always have accessible on their hip tied off by a cord.
The best part about gaff tape is that it is less likely to leave residue. When using Duct tape or regular clear tape you will often times find that it will leave sticky leftovers. When using gaff tape you have a much greater chance of having less to clean up, less hassles taking it off and a much cleaner location. It also has a few other tricks, gaff tape like duct tape is also water proof and rips very easily. All of which makes it easier to use on set.
**101 Uses for Gaffer Tape:
Some will say that you don’t have to worry about it leaving a sticky residue, however I will tell you, depending on the heat and how long and where the tape has been applied, it can and will leave a mess. It is much less likely and you should always think before applying any kind of tape.
Where should I buy Gaff tape? You can buy gaff tape almost anywhere online. Amazon has a variety of tape. Brands I use is SAVAGE. I find that they make high quality and long lengths of tape in which I have never had issues with.
Gaff tape comes in a variety of lengths, thicknesses, and colours. 90% of the time I use black 2” tape to tie down loose cables and fix broken camera gear. Like most filmmakers, I am always surprised just how much I use on every set. I would recommend bring a roll of black and white gaffers tape no matter the shoot. When you do not have it you are hurting on set.