Sometimes, when one is doing cable runs, one wants the ability to branch out and make a single cable into multiple cables – much like a power strip that you use in your house, only with a lot more power.
Enter the three-fer.
It allows us to plug three things into one cable. It’s usually used at a distribution box to allow the connection of an HMI ballast and some smaller cable (banded, as opposed to the heavy cable).
One has to be careful, though, as the three-fers aren’t rated for as much electricity as the cable and if overloaded can cause a fire.
Exactly like a power strip in your house, only with a lot more fire.
One of my greatest regrets in life was not having a video camera on The Night The Cable Caught Fire. It was *cough cough* years ago and the reactions of production (screaming, running around, tearing out of hair) compared to the reactions of the electricians (calmly walking to the shutoff and killing the power, then telling anyone who was in earshot about the *really* big fire they saw on another set) was priceless.