You run your mainline through your slip sinker then tie to your barrel swivel. Then tie your Powerbait/worm/lure/what ever you are using to the other end of the barrel swivel.

The idea, especially for Powerbait users, is for the fish to take the bait without feeling resistence from a chunk of lead sitting on the bottom. It can also be considered cotrolled depth fishing from the bottom up. This technique is very effective.