A striker for a lock, comprising: a receiving body having a housing suitable for receiving a locking member of a lock, said receiving body being insertable into a cavity fashioned on a supporting frame of a door or window; at least one retaining element associated with the receiving body and switchable from a release condition, in which the receiving body is insertable in said cavity , and a locking condition, in which said retaining element , after the insertion of the receiving body into the cavity , acts on an engagement portion associated with the supporting frame in such a way as to maintain the receiving body inserted in said cavity ; an abutting means for applying and transferring a force on the retaining element to make it switch from the locking condition to the release condition, so as to enable the receiving body to be removed from said cavity , said abutting means being positioned on a portion of the receiving body , which remains exposed when said receiving body is inserted in the cavity , and comprising at least one recess operatively associated with the retaining element and suitable for cooperating with a tool, wherein said recess is fashioned on a surface of the receiving body in a position adjacent to the retaining element , in such a way as to be at least partially delimited by a portion of the retaining element itself, said recess being conformed so as to enable the application and transfer of a force (F1) in a direction such as to induce an angular shift (S1) of the retaining element directed toward the inside of the housing by rotation about an axis passing through a centre of rotation associated with said retaining element , wherein said recess is positioned on a side of the retaining element opposite to the housing . a receiving body having a housing suitable for receiving a locking member of a lock, said receiving body being insertable into a cavity fashioned on a supporting frame of a door or window; at least one retaining element associated with the receiving body and switchable from a release condition, in which the receiving body is insertable in said cavity , and a locking condition, in which said retaining element , after the insertion of the receiving body into the cavity , acts on an engagement portion associated with the supporting frame in such a way as to maintain the receiving body inserted in said cavity ; an abutting means for applying and transferring a force on the retaining element to make it switch from the locking condition to the release condition, so as to enable the receiving body to be removed from said cavity , said abutting means being positioned on a portion of the receiving body , which remains exposed when said receiving body is inserted in the cavity , and comprising at least one recess operatively associated with the retaining element and suitable for cooperating with a tool, wherein said recess is fashioned on a surface of the receiving body in a position adjacent to the retaining element , in such a way as to be at least partially delimited by a portion of the retaining element itself, said recess being conformed so as to enable the application and transfer of a force (F1) in a direction such as to induce an angular shift (S1) of the retaining element directed toward the inside of the housing by rotation about an axis passing through a centre of rotation associated with said retaining element , wherein said recess is positioned on a side of the retaining element opposite to the housing . <EOS>