Shabbos, Chapter 17, Mishnah 8. This Mishnah has an explanation in the Gemara that helps us understand the precise parameters of the dispute it records. We will first read the Mishnah at face value, and then explain how the Gemara understands it and read its words back into the language of the Mishnah.
The words of the Mishnah:
"Kol kisui hakelim she'yesh lahem beis achizah" - all covers of vessels that have a handle on top of them, "nitalin lahem b'Shabbos" - may be carried on Shabbos. They are not considered muktzeh, and there is no concern of building involved in them.
"Amar Rabbi Yosi: b'meh devarim amurim" - when is it true that covers of vessels require a handle, and without one they may not be carried? "B'kisui hakarka'os" - regarding something that covers an item in the ground, which is liable to be considered actual building rather than the cover of a vessel, and therefore it requires a handle to show that it is not permanent but is meant to be removed and replaced.
"Aval b'kisui hakelim" - the cover of a pot or of an ordinary vessel, "bein kach uvein kach" - whether it has a handle or does not, "nitalin lahem b'Shabbos" - for it is clear that this is not building and is not meant to be part of any structure, but rather to be removed and replaced, even without a handle.
The Gemara's explanation:
The Gemara explains that two extremes are not subject to any dispute at all:
The covers of vessels themselves - a box, a pot and the like: even the first Tanna agrees that the cover does not need a handle in order for it to be permitted to carry it. Although his wording implies that a handle is required, he is not speaking about this case, and here everyone agrees.
A cover of something in the ground itself - that which covers something that is part of the ground: it certainly requires a handle, and in this too everyone agrees.
The point of dispute:
The dispute revolves around a vessel that is attached to the ground:
The first Tanna: a vessel attached to the ground - its cover requires a handle, and without one it may not be moved, because it looks like building, since the vessel is attached to the ground. This is his intent when he says "Kol kisui hakelim she'yesh lahem beis achizah" - meaning, covers of vessels attached to the ground that have a handle - "nitalin lahem b'Shabbos", and it is permitted to carry them.
Rabbi Yosi: even vessels attached to the ground do not need their covers to have a handle in order to carry them. This is his intent: "B'meh devarim amurim" - when is a handle required? "B'kisui hakarka'os" - regarding a cover of the ground itself, such as the cover of a hole in the ground. "Aval b'kisui hakelim" - covers of vessels attached to the ground - "bein kach uvein kach", whether they have a handle or do not, "nitalin b'Shabbos".
In summary: the Mishnah deals with three levels: the cover of an ordinary vessel, which everyone permits carrying even without a handle; a cover of the ground itself, for which everyone requires a handle; and the cover of a vessel attached to the ground - and about this the first Tanna, who requires a handle because it looks like building, and Rabbi Yosi, who permits carrying it either way, disagree.