Hi. Can the two halves of these clips be separated? One has fallen away off the parcel shelf (common problem) and if I can separate the two halves then I can re-install it on the shelf. But I have tried everything like trying to prise it apart while pushing the serrated grip sideways and other similar things. It seems that they are “one-use” and can never be re-used. Is this correct or can you take them apart? It is a 66 plate C-Max. Thanks.