Trout move deeper in the water column to seek out cool water as summer sets in and surface waters warm. Trout often inhabit depths around the thermocline, the transition between the warm, oxygenated surface layer and the cool, low-oxygen lower layer. Use leadcore line to present baitfish-imitating crankbaits and spoons in the depth zone trout are inhabiting. As a general rule, each color on the leadcore line (about 30 feet) adds 5 feet of depth to the presentation. Tie on a 6- to 10-foot leader and attach the lure with a cross-lock snap. Troll at 2 to 4 mph over deep structure and along steep breaklines.