Laws of Muktzeh on Shabbos
7. An object that is not considered a utensil ("K'li"), for example,
pieces of wood, stones, pieces of metal and the like, are also forbidden to
be handled at all on Shabbos, even to use the body of the object for a
permitted purpose or because one requires it's place; [this prohibition
applies] unless one has set them aside on Friday to be permanently used for
a particular purpose (1).
Therefore, it is forbidden to take, [on Shabbos], a sliver of wood to use
as a tooth pick. Candles that are not whole (2) are not considered utensils
and are forbidden to be handled for any reason. Similarly, a ladder used
for climbing to the attic is not considered a utensil (3).
(1) Where one intends to use these items in a way that is commonplace, one
does not have to set it aside for more than one Shabbos. If one is setting
aside an object for permanent use, then a mental resolution before Shabbos
would suffice. However, if one is designating it for temporary use, a
mental resolution is not sufficient; rather, one must make a small physical
change in the object before Shabbos ("Muktzeh: A Practical Guide" by Rav
S.B Cohen; see also Mishna Berura 308:97 for details and exceptions).
(2) That is, not fit to be lit.
(3) There is a dispute among the authorities as to when and why this sort
of ladder would be considered Muktzeh.