They use a shower curtain hook as a slide on the anchor line and a rubber band tied to the baited line hooked in the shower curtain hook. The baited line is usually lowered on the anchor line until the live bait just touches the water and struggles to go deeper. When the fish hits the bait the rubber band breaks and you are just fighting the fish.
Sometimes they weight the curtain hook also.
Make sure you use a spider weight on the anchor line so it will dig into the sand or it will not hold solid.
"Many men go fishing all of their lives without knowing that it is not fish they are after." By Henry David Thoreau.