I’ll focus on the actual process of finding productive rock piles.
Because the rock piles I’m talking about are not visible above the surface, a great deal of time may have to be invested before finding one that draws groups of bass.

When I was first learning Lake Minnetonka’s rock piles, a 14,000-acre lake near my home in Minnesota, I considered it a good day if I found two productive piles. And some days, I wouldn’t find any.
Anytime you are dealing with subsurface structure, the first place to start is with a contour map of the lake. However, many anglers overemphasize the use of maps especially when natural lakes are involved. By that I mean they expect to find on the map precise locations to fish. That’s not so, but maps do give us a place to start.
Reservoir maps are generally more detailed than maps of natural lakes because they have had the opportunity of being mapped before the lake was filled. Natural lakes on the other hand, often have many pieces of structure omitted from them because mapmakers simply didn’t find them. I rely on maps simply to aid in navigation about the lake and also to provide a broad picture of the lake’s bottom. I can see where many of the large flats are located and where major creek channels run. However, for the most part, the rock piles I’m looking for will not be shown on the map. If there are rock piles indicated, typically, they are community holes fished by everyone.
Do-It-Yourself Mapping
For these reasons, searching out productive rock piles basically comes down to conducting a do-it-yourself mapping of the lake using your boat’s electronics. I do my searching/mapping using Zercom’s Classic In-Dash flasher and also its new LPG2000 graph. These are quality products that are necessary when trying to detect subtle differences in bottom composition.
To do your own searching/mapping, first start with a map to find a flat or area of the lake that is appropriate for the season at hand. Next, as we discussed last week, a sharp contour change needs to be found along this flat along with the rocks themselves. So, simply take your boat and begin zigzagging across the drop-off, keeping an eye on your electronics. On a new lake, I like to take a lot of time with this process before starting to fish. That way, I have a much better understanding of the bottom composition and the general sharpness of the drop-offs. I don’t worry so much about marking bass on my electronics although the marking of baitfish can be very important in certain lakes/situations.
After spending this time with the electronics, hopefully somewhere along the way, a sharp drop and good rock pile have been found together. I’ll return to likely looking spots and then begin fishing. Rapala Down-Deep crankbaits, Carolina-rigs, and Roll’r jigs are my baits of choice for rock piles. These baits track along the bottom transmitting precisely what is there. The “feel” these baits provide are extremely important in detecting subtle changes (differences in rock size, composition, and quantity) in the bottom. For it is these irregularities that typically serve as holding places for the bass. Structure having rock of uniform size and distribution, generally won’t group the bass nearly as tight.
Well that’s about all there is to it. It sounds simple, but finding bass on submerged rock piles can be one of the more difficult tasks for fishermen to do. Large amounts of time are often required and patience is tested. But when the bass are found, action can be fast and furious and you will catch some of the biggest fish in the lake to make it well worth the time you put into it.