No, not talking about some hardware tool.  This is a special kind of elastic, but not some dainty chipmunks.

We’re talking super strong rubber band that’s been strung across ALL my lower brackets and immediately started squeezing my lower teeth together.  It was only mushy food for a couple of days.  (See photo below — click to larger image. ) The chain is silver colored, which blends in nicely. 


Why this particular form of dental torture?  Because I pointed out the gap between the molars (a question I had earlier), and the power chain is how they close the gap.  Below is a photo of the gap; you can see the power chain stretched between the brackets.


For more details on power chains and how they work, read this thorough description.