6. Utensils that a person would not consider using [for anything other than
their primary function] out of a concern that they might get damaged, fall
under the category called "muktzeh machamas chesron kiss" ("muktzeh due to
[potential] financial loss"); examples include: professional tools which
one is careful not to damage, a knife used to sharpen a quill, a
specialized slaughtering knife, a knife used for circumcision (1), paper
that is set aside to be used for writing, promissory notes, accounting
ledgers, letters that one saves, valuable items that one never uses, and
any other item that one is careful to protect and therefore designates a
specific place for it, and doesn't use it at all (2).
[This category] also includes items that are in a shop ready to be sold,
even if they are eating utensils, if the owner never lends them out
(however, if they are sometimes lent out, they are not muktzeh) (3). All
the aforementioned articles, and anything similar to them, including a
wallet or purse, are considered "muktzeh machamas chesron kiss," and may
not be handled even to use the body of the object for a permitted activity
("Tzorech Gufo"), or because one needs the space they are resting in
(1) Performing a circumcision is permitted on Shabbos. This halacha is
obviously referring to moving it for some other purpose.
(2) Like a precious work of art.
(3) Food, however, which is set aside for sale, is not considered muktzeh.