crappiepappy is right on give the fish options in the area. my lake goes up and down so i try to keep a 4' window from normal pool if it drops 3' under during the winter they are still good cause if they pop out on my lake they get hammered or drug off. as for the blocks cut up some good hard wood brush stuff with maybe a 5' x 5' circumference trim them to the heart of it like 2" diameter and bigger they last longer and hook them to a block and sink them like has been mentioned if you use the heavier part of the tree it also makes it easier to handle.