What a slider float is
A slider float is not held on the line: the line passes through its eye or an internal tube, and the float runs freely along it. The depth is set not by the float but by the stop above it.
How it removes the depth limit
On the cast the float lies by the lead and the whole rig is compact — easy to lift clear of the water even at a big fishing depth. In the water the weight pulls the line down, it runs through the eye, the float rises and comes up against the stop.
Because of that the fishing depth no longer depends on the length of the tackle — something a fixed float cannot do at all.
The stop sets the depth
The stop is a knot tied from line, or a silicone fitting on the mainline. Slide it up and you fish deeper, down and you fish shallower, and it takes seconds by hand, without rebuilding the rig.
The knot here works as a limiter, not as a join, and the demands on it are different: it has to hold and to slide at the same time. Knots in tackle are covered separately — what a fishing knot is.
What the bead is for
The eye of the float is bigger than the stop knot, so without a bead the stop simply passes through it and the depth never sets. The bead is bigger than the knot and smaller than the eye — that is what stops the float.
This is not an accessory but a condition of the rig working: without it a slider float does not work at all.
Why the weight cannot be made light
The line has to draw through the eye under the weight of the rig. A light weight does not do it: the float lies flat or stays where it is, and the depth is never set.
It looks like “the float will not go down”, and the cure is not a different float but a heavier weight. In this the slider is the direct opposite of the fixed float, where the weight is cut back almost without limit.
What gets in the way in practice
The stop has to pass through the rod rings and the line roller of the reel. An oversized knot bangs against the rings and slows the line on the cast — casting range drops and the knot itself wears faster.
The second thing is time. The float does not cock instantly: for the first seconds after it lands the rig is still settling, and a bite at that moment does not read.
What we do not write here
How long to make the stop knot and how many turns to put in. That depends on the diameter of the line and on the rings of the particular rod, and we have not found a verified source for general figures.