Library-book or -materials vandalism, sometimes termed intentional destruction of books or materials or book or material mutilation is the act of damaging or defacing library books or other library holdings. It is a considerable loss of resources for libraries with high rates of vandalism. As with book theft at libraries, vandalism of books has been studied by a number of library professionals. Librarians consider book vandalism and mutilation a "threat to intellectual property" and have seen it as a "tremendous challenge to the library profession worldwide." Handwriting or marks in and tearing or removal of pages from books can all be forms of vandalism or mutilation. Arson is another form of library book vandalism. The hiding of books within libraries is sometimes considered to be a form of materials vandalism.