Tool for linking open fastener

To increase strength, decrease the number of components, and simplify the structure of a bottom stopping member, and to cause the linking of bottom stopping members and the pulling up of a slider to be simple and reliable. An engagement member (13) of a bottom stopping member (10) is configured from: a base-side member (14) provided with an insertion section (143) and a housing section (142); a lid-side member (15) provided with an insertion section (153) at which a cylindrical section (154) is formed, and a housing section (152) that, together with the housing section (142) of the engagement member (13), forms an elastic body housing space (S); and an elastic body (16) that is housed in the elastic body housing space (S). A box body section (18) is such that an engagement section (201) is formed within an insertion hole (20), the insertion hole (20) has an inner space at which an assembly of the insertion sections (143, 153) of the engagement member (13) can rotate centered on the alignment point of the enga