No, theymeasure level over their entire length, in the case of spirit levels
No, they don't.
Here is an example of a spirit level:

It measures for level in that small section in the middle.
It does this with a approximately cylindrical container, mostly filled with fluid.
It measures level by that fluid going to the bottom of the container, leaving a pocket at the top.
i.e. it measure as perpendicular to down, at that point.
That is all it does.
You then have a piece of metal (or some other material) attached to it, with faces far too inaccurate to detect the curvature of Earth along them.
But notice how you don't even bother responding to what I said?
I said they measure level as perpendicular to down. As that is what they do.
Instead of even attempting to address that you instead want to focus on if they measure that at a single point or along a length.
And of course, even that is just to try and deflect away from the far more important issues.
Once more, see if you can answer this simple question:
Here is a simple diagram for you:

This is a mountain on a RE.
On this mountain, on a RE, which way do you think is down?
Do you think it is A, or do you think it is B?
First of all, you know I'm referring to standard spirit levels, with one tube in the middle. Don't play the weasel here, it won't work.
Standard spirit levels with one tube in the middle, measure over their entire length, for level, right? So when we put it atop a mound's peak, and balance it along the peak, it measures LEVEL, right? But we know the mound is NOT level, so it is NOT measuring for level, over the length of that instrument.
We must measure for level OVER the entire length of the instrument, to find if something is level, or is not level.
Standard spirit levels with one tube in the middle, have a flat, straight edge on them, or at all it's edges, which are used to measure for level, right?
Why? Because levels are measuring for a flat, straight, horizontal surface, along their flat, straight edges, which we put down on surfaces, to see if they ARE level, ARE flat, ARE straight, and ARE horizontal, along their edges.
How could they ever TRY to measure for a CURVE? They have a flat, straight edge on them, which we place on surfaces! How could they measure for any sort of CURVE, using flat, straight edges to measure for LEVEL?
Even if Earth HAD a 'curve' over it's surface, levels could NOT measure for it, having a straight, flat edge on them! It's insane to even say such a thing is done, let alone ever POSSIBLE!
These instruments can only measure over their length, except for laser levels, which measure over distances outward from the instrument itself, by a laser light cast outward. Even they are limited in distance measured, too.
They do NOT measure for a curve, any curve, of any degree of a curve. They couldn't, even if we TRIED to use it to measure for a curve. No way, no how, it is simply impossible to do such a thing.
And what IS perpendicular to level, is at 90 degrees to it, and is exactly VERTICAL to level.
Vertical is a straight line, perpendicular to a HORIZONTAL line, which is also straight. And it is called LEVEL.
When those liars said Earth was a ball, speeding around in endless 'space;, they were well aware it had problems which were impossible to explain away as being a curved surface on a ball Earth. It was done with trickery, and said we shall take the word of our 'experts', who are a bunch of well paid liars, and frauds, but are intelligent, and clever, making them perfect liars, who know enough to look legitimate and trustworthy for claiming things without any proof, or confirmation of their claims, by others, which is why it is NOT any sort of actual science, which is entirely based on being honest, and open, to others, confirming all their claims, and using their instruments, that WERE used for their claims, exactly as it is done, with ASTRONOMY.
They've made countless claims, and never allowed us to prove or confirm any of them.
Not science, it's BS, an ANTI-science - that's blatantly obvious to see, isn't it?