Black "Gaffers tape" is a tape designed to hold things temporarily and be removed without leaving a residue (or as little residue as possible). You can tear off

Black "Gaffers tape" is a tape designed to hold things temporarily and be removed without leaving a residue (or as little residue as possible). You can tear off a perfectly square piece with your fingers since the fabric of the tape is aligned with the tape. It's great for covering those always on LEDs. It is better than electrical tape for this purpose IMO.