The invention relates to a device (1) for holding together, adjusting, fitting or fastening parts of a garment, shoe or any other accessory. It contains a first part (2) comprising a sheath (3) in which a first magnet or ferromagnetic element (4) is inserted, these being movable inside the first sheath, and a second part (5) containing a second magnet or ferromagnetic element (6) subject or submitted to the magnetic attraction of the first magnet or ferromagnetic element of the first part, and is used to hold together, adjust, fit or fasten the garment, shoe or accessory when one of the said first and second parts (2, 5) is activated by a user to work in conjunction or alterations is thus possible through the sliding (7) of the first magnet or ferromagnetic element (4) in the first sheath (3).