Downrigging is a method of trolling that uses a manual or electric winch and weight (cannonball) to carry your fishing lines and lures to a specific depth, where feeding fish are to be found. While downrigging is commonly thought of as a deep water fishing technique, it is more accurately understood as a method of "controlled depth fishing"

By using downriggers to control the depth of your lure presentation, you can place your lures at any depth from just below the surface to 200 feet deep and keep them running consistently at that depth. So, once you've determined what depth the fish are feeding at, you can keep your lures in that "feeding zone".

When a fish takes your lure, it will pull your fishing line from the line release. This will allow you to fight the fish, without fighting a heavy weight.
Step-By-Step Operation Of A Manual Downrigger
While the boat is running at trolling speed, set your fishing reel to free-spool, apply slight pressure to the reel with your thumb and let your lure out to the desired distance. Then set the drag clicker to stop your reel from free-spooling. Now, place your fishing rod in the rod holder.
Next, take hold of the fishing line (beyond the rod tip) in one hand. With the other hand, reach down and firmly take hold of the line release. Lift the cannonball out of the water and attach the line to the line release. Then ease the cannonball back into the water.
While firmly gripping the downrigger reel's handle, loosen the clutch knob (found on the right side of the downrigger) by turning it counter-clockwise. This will release the tension on the clutch disc plates that holds the cannonball at a given depth.
When you feel the weight of the cannonball pull on the downrigger reel, crank the reel counter-clockwise to lower the cannonball. Watch the line counter that is mounted on the top of the downrigger. The line counter is marked in one foot increments.
After you see the depth you desire marked on the line counter, retighten the disc clutch by turning the clutch knob clockwise until the clutch holds the weight of the cannonball.
Once you've set the clutch on your downrigger, set the drag and drag clicker on your fishing reel. Then take up the slack in your in your fishing line, until there is a bow in your fishing rod.
When a fish strikes or when you want to retrieve your lure, remove your fishing rod from the rod holder and abruptly lift it to release your fishing line from the line release. Then fight and land your fish or retrieve your lure.
Finally, to retrieve your cannoball, firmly grip the downrigger reel's handle, loosen the clutch knob and crank the downrigger reel clockwise until the cannonball surfaces. Then tighten the clutch knob to hold the cannonball securely.