Helicopter Hook Rig
I never see this rig used on a regular basis, therefore it is one which could work on waters that are heavily fished:
To setup the helicopter rig you do not tie the hook on. The idea is that the hook is free to spin around on the hooklink, and this enables it to take hold in the carps mouth as soon as the line is tightened on the strike. The way the hook is attached acts as a line aligner, and the hook bites home every time. This hook rig only works in conjunction with a stiff link, for example stiff nylon, and the larger the hook the better, for example a size 4 is ideal. The reason for the large hook is due to the large eye, which allows the hook to swivel more freely. This rig should only be used with a critically balanced bottom bait, as it counters the weight of the hook and hooklink. Place a float stop on the link, then thread the hook on. Tie a secure knot in the end of the link, then super glue to ensure it holds. The knot will need to be much larger than the eye of the hook, to ensure the hook will not fall off. At the other end , tie the swivel on with a loop knot so that the link is free to move at that end, thus increasing movement.