Laws of Muktzeh on Shabbos
5. [The following laws apply to] utensils whose primary function is to perform an activity that is forbidden on Shabbos (1), for example, a mortar, a mill, a hammer, a hatchet, a broom (2), a shofar, a candelabra, a sowing needle, whole candles made from either tallow or beeswax, cotton wicks, or a garment containing sha'atnez (3), which is forbidden to be worn.
These articles, and those similar to them, may be handled on Shabbos only when the body of the utensil is needed for a permitted activity ("l'tzorech gufon"); for example, a hammer may be used to crack open nuts, a hatchet to cut food, or a needle to remove a splinter (this is true only when the needle is whole; if its point or eye is broken off, it may not be handled). Similarly, such articles may be moved if the space in which they are resting is required for another purpose ("l'tzorech mekomon") (4).
After picking up such an article for one of these two reasons, or if one forgot and inadvertently picked up such an article (5), one may carry it further away and place it down wherever one desires. These articles may not, however, be handled for their own sake, for example, to protect them from being stolen or destroyed (6).
Tefillin are also forbidden to be handled . If, however, they are left in a degrading place where they might become dirty, they may be picked up and put in a safe place (7).
(1) This type of utensil is called a "kli She'melachto le'issur."
(2) A broom was considered a member of this category of utensils only at a time when most homes had dirt floors; it was forbidden to sweep the floor on Shabbos because one might level out a hole, and violate the prohibition against "plowing" (any activity that improves the soil for planting is prohibited under that category).
(3) That is, a garment containing a mixture of wool and linen.
(4) The permission granted to handle an object for the two reasons mentioned, only applies to objects that are defined as "Kelim," that is, usable utensils; however, things which have no inherent function, such as pebbles or bones, may not be handled at all (they are classified as "muktzeh machamas gufo," or "inherently muktzeh"). Utensils which have a function, but have no permissible function on Shabbos, may be handled for the two reasons mentioned, only in cases of necessity (See "Muktzeh: A Practical Guide" by Rav S.B Cohen, pg 18).
(5) Some authorities rule that if one inadvertently picked it up, one must put it down immediately (Vilna Gaon).
(6) In cases of great financial loss, one may place a non-muktzeh item, such as bread or silverware, on top of the object, and carry them together (Shulchan Aruch HaRav 308:22).
(7) They may also be moved to prevent them from being stolen (Pri Megadim).