The function of a lead sinker:

When fishing for freshwater, the lead sinker is an essential weight that makes the hook sink to the bottom, stabilizing the bait at the fishing spot, making it easier for fish to feed on the bait; it also allows the fishing line to be tautly vertical in the water, producing high sensitivity.

When using a casting rod for fishing, one can also take advantage of the weight of the lead sinker to cast the hook and bait far away. Working in conjunction with the float, it allows the hook and bait to hang suspended at the desired water level or to sink rapidly to the bottom.

In dynamic water, the weight of the sinker ensures that the hook and bait are not carried away by the current. Another advantage is that the sinker can indicate the float, helping to detect the depth of the water and the conditions at the bottom.