This simple device is meant to help straighten out 8 3mm LEDs on a breadboard. When they are placed next to each other, they tend to get out of line, and sometimes even out of order. Slide this on (I needed to use tweezers to get the LEDs in the holes), and it keeps them all in order in a nice straight line for you.

I've included a before and after photo so you can see how it helps.