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 (101, 201) fashioned on a supporting frame (100, 200) 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 (101, 201), and a locking condition, in which said retaining element, after the insertion of the receiving body into the cavity (101, 201), acts on an engagement portion associated with the supporting frame (100, 200) in such a way as to maintain the receiving body inserted in said cavity (101, 201); 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 (101, 201), said abutting means being positioned on a portion of the receiving body, which remains exposed when said receiving body is inserted in the cavity (101, 201), 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 in a direction such as to induce an angular shift 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 (101, 201) fashioned on a supporting frame (100, 200) 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 (101, 201), and a locking condition, in which said retaining element, after the insertion of the receiving body into the cavity (101, 201), acts on an engagement portion associated with the supporting frame (100, 200) in such a way as to maintain the receiving body inserted in said cavity (101, 201); 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 (101, 201), said abutting means being positioned on a portion of the receiving body, which remains exposed when said receiving body is inserted in the cavity (101, 201), 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 in a direction such as to induce an angular shift 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.