0.33333... *is* a precise value. We just don't write all the 3's because we don't have infinite time but, mathmatically, that's *exactly* 1/3.

And we can easily plot that on a numberline. Take a line of length 1, bend it around until it forms an equilateral triangle (angles exactly 60 degrees), mark the corners, unfold it. Those marks are at *exactly* 1/3.

If you mean "can we do this in real life" the answer is "no" but that has nothing to do with the math, that has to do with our physical universe being discrete(ish) at very small scales. Number lines are purely theoretical constructs in the first place, the fact that we run out of good measuring tools with a physical number line doesn't change the math.