To provide a tool for preventing a book's band from becoming out of place as when a person picks up a book and opens the cover at a bookstore, there is a problem of a band bound at the lower part of the jacket covering the cover of the book coming off or slipping out of place in a vertical direction.

A tab for sticking is provided at a long side of one side of a conical-shaped bag whose tip part is cut and on the rear side of the tab for sticking an adhesive which is able to repeatedly fasten and detach is applied.