A mechanism for fixing together first and second parts and comprising first and second guides provided respectively in or attached to the first and second parts. The mechanism further comprises first and second magnetic components coupled respectively to the first and second guides such that the first magnetic component is rotatable with the first guide and the first part, and the second magnetic component cannot rotate relative to the second guide, the magnetic components being moveable axially and rotationally with respect to each other and having magnetic poles oriented such that rotation of said first magnetic component causes relative axial movement of the magnetic components between a locking position in which one of the magnetic components straddles the two guides and an unlocking position in which it does not straddle the two guides.