What it is
The lift is older than most of the people fishing it. You fish a bait on the silt, slightly overdepth, with a small shot a few inches from the hook. When a tench picks the bait up, the shot comes up, and the float rises or lays flat.
Strike that. It is not a dip. It is the opposite, and it still catches more tench than a quiver tip on the right peg.