During the hot summer months when the slab bite can get slow at best and you can read your sonar and see fish stacked up on the bottom, what is happening is this, the fish aren't hungry and won't rise up and bite a slab but if something wiggles past them like a pet spoon trailed behind a Hellbender or Jet Diver or anything that can get a bait down to 15 ft. will work.
Here is how I do and for those of you that have fished with me before you should have pleasant memories of the damage that can be done by fishing this way. First take the hellbender, most of the time when you buy one 2 treble hooks will be attached to it, screw them out, I put the screw with hook attached in a vice and then use a pair of longnose pliers to bend the screw to be able to get the hook out, which we discard both hooks, then attach a 3/4 oz. crappie weight to front screw, bend it back straight and re screw it into the front hole of bottom of hellbender. Now gently bend the lip of the hellbender slightly to make lip bend down a little past straight, not too much but it will enable hellbender to dive even deeper. Now take about 4 to 6 ft. of line and attach it to the rear of the hellbender and tie on a a petspoon or smething similiar, crappie jigs will work but are easy bendable and will lose large fish, small rooster tails will also work but hooks are so small and many fish are also lost.
Now before you start trolling drop bait about 8 ft. behind boat and put engine into forward and go about 5 mph see how bait is trolling if it is pulling hard to either the left or right, take a pair of pliers and bend the eyelet on the lip of hellbender the opposite direction, experiment until it runs straight.
Now for the trolling part, if your in 15 ft. of water let out about 15 seconds of line or about 45 -50 ft., you don't want to be banging bottom or you will get hung up a lot and lose baits and they are not cheap. If your in 20 ft. of water let about 20 seconds of line, you should get the idea by now. If you are on a hump make you sure you start out about 50 ft. from crest of hump, that way your baits will be all of the way down before you hit the crest of the hump, watch your sonar and when you see fish marks, hold on!