Here's a fat closed-cell foam hopper built with a translucent drinking straw
between body and shank. If you bend an s-loop into the butt section of your leader,
and then feed that s-loop through the straw, you can then pull the loop (that appears
at the rear end of the straw) up and over the body of the hopper.

Tension at both ends of the line pulls the loop tight around the body, enough so you can
actually catch a fish on the hopper. But if you hold the hook in one hand, and then jerk
on the tippet end of the leader, then the knot loosens up, which allows you to adjust
the bobber-hopper's position up or down the leader, as needed.

http://montana-riverboats.com/Robopa...-bobber-hopper