Agree with Intimidator; we have also found putting them in sets from shallow to deep and with 6 to 15 attractor per set (depending in the bottom contours). Also mixing a variety of types can help make them 2-3X more productive, with "BB"s (brush blocks) with long lasting HARDWOOD limbs shallowest in 6-10 fow, "C" trees deeper and lastly PVC deepest of all. Doing this helps create about an ideal mixture of cover for almost everything that swims, from minnows, juvenile fish, and "big uns". Many species will probably take advantage of this variety through out the year, and they will likely hold fish even as cold fronts roll through...