<div>Regarding the linguistic terminology (Muktzeh= set aside) and theory of Muktzeh, it is very important to note that there is a dispute between R' Yehudah and R' Shimon in the Gemara as to whether Muktzeh applies on Shabbos at all, with R' Shimon holding that it does not, and that is how we Pasken! </div>
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<div>The Aruch Hashluchan in the beginning of OC 308 explains that the dispute between R' Yehudah and R' Shimon revolves around the point raised - RY holds that anything which is not actively designated or assumed by its nature/function to be for a permitted Shabbos use is Muktzeh, whereas R' Shimon holds that anything which is not actively rejected (Lo Chazi+Dochui B'yadayim) is assumed to be Muchan, unless it is something which has no designated use whatsoever.</div>
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<div>It is also not at all Pashut that Keli SheMelachto L'Issur is a function of Muktzeh in the sense of designation or lack thereof. It may be a separate Gezeirah where there is concern that one might come to use it in a prohibited fashion, and it isn't that there was a <strong>relaxation</strong> of Muktzeh in terms of allowing the movement of a Keli Shemelachto L'Issur L'tzorech Gufo UMekomo, but there was never any Gezeira on such a thing in the first place. See GRA to YD 266. This can explain, e.g., the dispute whether a KSHML"A can create a Bosis.</div>