SUMMARY: The Gemara discusses the final ruling with regard to Muktzah, and it teaches the Halachah with regard to several basic categories of Muktzah.
(a) Muktzah Machmas Mi'us (the object is repulsive): The Halachah follows the view of Rebbi Shimon that such objects are permitted and are not Muktzah.
(b) Muktzah Machmas Isur (the object could not be handled during Bein ha'Shemashos without the person transgressing a prohibition of Shabbos): TOSFOS (here, and 19b) says that we are also lenient like Rebbi Shimon with regard to this type of object, unless the person actively put the object in a situation in which it could not be handled during Bein ha'Shemashos.
The ROSH and TUR, however, do not mention such a condition, and they rule simply that Muktzah Machmas Isur is prohibited in accordance with the view of Rebbi Yehudah.
(c) Muktzah Machmas Chisaron Kis, and Grogeros v'Tzimukin (objects that a person actively put into a situation where they would be unfit to be used for Shabbos): Even Rebbi Shimon agrees that these objects are Muktzah, and this is the Halachah.
Although this is the Halachah with regard to Shabbos, some Rishonim maintain that with regard to Yom Tov the Halachah differs (see Insights to Beitzah 2:2). (For a comprehensive summary of the various types of Muktzah and the opinions regarding them, see Insights to Beitzah 2:1.)


OPINIONS: The Mishnah relates an incident in which a certain type of pitcher was tied to a type of reed-string in order to measure the opening of a barrel on Shabbos. The Gemara explains that the Mishnah refers to a case in which a small "Hilketi" separated between two houses and the Tum'ah of a Mes was present.
What exactly is a "Hilketi," and what measurements were made with regard to the Tum'ah in this case?
(a) RASHI explains that a Hilketi is an alley between two houses. A cracked barrel rested above the alley, supported by the walls of the two houses on each side of the alley. The barrel formed the ceiling of the alley. A Mes (or, more specifically, a piece from a Mes the size of a k'Zayis) was lying in the alley directly under the cracked barrel.
The crack was measured in order to determine whether its width was one Tefach, which would allow the Tum'ah of the Mes to go straight up, and out, without conveying Tum'ah to the houses on each side of the alley through their windows. If the hole in the barrel was less than a Tefach, the Tum'ah would be prevented from exiting and it would spread throughout the entire area in the alley underneath the barrel, and it would enter the houses through the windows.
However, Rashi asks that this explanation does not seem to be consistent with the Mishnah in Ohalos that states that even if the crack above the Tum'as Mes is less than a Tefach wide, the Tum'ah exits through the crack and does not spread beneath the Ohel.
(b) TOSFOS explains that the Mes in the alley was lying under the solid part of the barrel and not under the crack in the barrel. The question was whether or not the crack, which extended across the entire length of the barrel, prevented the Tum'ah from passing to the other side of the barrel, from where it would continue through the windows into the houses.
This is consistent with the Mishnah in Ohalos that says that if there is a one- Tefach-wide break in the ceiling, Tum'ah does not spread from one side to the other across the break, but if the crack is less than a Tefach, the Tum'ah does spread to the other side of the crack.
(c) RABEINU CHANANEL and the ARUCH explain that a Hilketi is a natural mound which forms the wall between two houses. It is not an alley at all. A Mes was in one house and there was a cracked barrel in a window in the Hilketi (the mound that served as a dividing wall) between the two houses. The barrel was measured in order to determine whether the barrel's opening was as large as a Tefach, in which case the Tum'ah would spread to the other house, or whether it was less than a Tefach and the Tum'ah was confined.