Gaffer tape is a very strong, cloth based tape that looks somewhat like duct tape, but isn't. It was originally developed to tape small light fixtures (like Lowell lights) to walls and doors in tight locations, so that it holds good but comes off pretty clean (if you don't leave it on forever). I work in a building that includes a theater, and our theater crew uses both black and white gaffer tape to taping down runs of cables, taping down dance floor and junk like that. I use it to tape electrical cables down to the floor, to hold seamless background up against a wall, and whenever else I might need strong tape.
I just popped over to Calumet's web site at http://www.calumetphoto.com/ and using speed search, I typed in "gaffer" and found: Gaffers Tape 1" x 60 Yards Black $6.49 Gaffers Tape 2" x 60 Yards Black $11.49 They also have grey and white. BTW, the Gaffer is the head lighting guy on a film or video shoot.
