Closing/locking device (1000, 11000, 12000) for closing a door and/or a window with respect to a jamb, comprising: a first part (1100, 2100, 7100, 9100, 10100, 11100, 12100) mountable on one between the door and/or window and the jamb, a second part (1200, 3200, 4200, 5200, 11200) mountable on the other one between the door and/or window and the jamb, wherein the first part (1100, 2100, 7100, 9100, 10100, 11100, 12100) comprises a male locking element movable with respect to the first part (1100, 2100, 7100, 9100, 10100, 11100, 12100), wherein the second part (1200, 3200, 4200, 5200, 11200) comprises a female locking element and a magnet, wherein the closing device (1000, 11000, 12000) is configured in such a way that the male locking element is attracted by the magnet towards the second part (1200, 3200, 4200, 5200, 11200), wherein the first part (2100, 7100, 9100) further comprises holding means configured so as to prevent the male locking element from moving back into the first part (2100, 7100, 9100) following the extraction of the male locking element from the first part; the closing/locking device (1000, 11000, 12000) being characterized in that: the holding means comprise: - an element with variable cross section having a cavity with variable cross section, - a movable element positioned at least partially within the cavity of the element with variable cross section, - one or more interference elements positioned between the element with variable cross section and the movable element, and - a retaining element (2124, 7124) configured so as to retain the one or more interference elements. a first part (1100, 2100, 7100, 9100, 10100, 11100, 12100) mountable on one between the door and/or window and the jamb, a second part (1200, 3200, 4200, 5200, 11200) mountable on the other one between the door and/or window and the jamb, wherein the first part (1100, 2100, 7100, 9100, 10100, 11100, 12100) comprises a male locking element movable with respect to the first part (1100, 2100, 7100, 9100, 10100, 11100, 12100), wherein the second part (1200, 3200, 4200, 5200, 11200) comprises a female locking element and a magnet, wherein the closing device (1000, 11000, 12000) is configured in such a way that the male locking element is attracted by the magnet towards the second part (1200, 3200, 4200, 5200, 11200), wherein the first part (2100, 7100, 9100) further comprises holding means configured so as to prevent the male locking element from moving back into the first part (2100, 7100, 9100) following the extraction of the male locking element from the first part; the closing/locking device (1000, 11000, 12000) being characterized in that: the holding means comprise: - an element with variable cross section having a cavity with variable cross section, - a movable element positioned at least partially within the cavity of the element with variable cross section, - one or more interference elements positioned between the element with variable cross section and the movable element, and - a retaining element (2124, 7124) configured so as to retain the one or more interference elements. - an element with variable cross section having a cavity with variable cross section, - a movable element positioned at least partially within the cavity of the element with variable cross section, - one or more interference elements positioned between the element with variable cross section and the movable element, and - a retaining element (2124, 7124) configured so as to retain the one or more interference elements.