A clip for holding first and second parts together snaps into an opening in a first part and includes a central housing for receiving and retaining a male portion on a second part using catches. The clip has a spring structure allowing sideways displacement of the catches so that it occupies either a locked position in which it projects into the central housing to prevent axial movement of the male portion, or a position of release of the male portion in which it is withdrawn from the central housing. The clip also includes a mechanism for causing the catches to move to their locked positions automatically by snapping the clip onto the first part.