Halacha distinguishes in this regard between ladders used primarily for construction and house repair, and ladders used indoors for purposes such as reaching the top shelves of bookcases and the like. Ladders used mainly for activities that are forbidden on Shabbat, such as construction, are indeed deemed Mukse on Shabbat and may not moved. By contrast, stepstools and other kinds of smaller ladders that are used for permissible purposes, such as reaching for books, do not have the status of Mukse on Shabbat. One may therefore move such a ladder on Shabbat for any reason, even to protect it, such as bringing it inside to protect it from the rain. (Menuhat Ahava, Helek 1)
