The rear reg plates are fixed on with rivnuts .And are fitted with a special tool , but can be fixed in with a piece of all thread nut and washers . It is to squash the rivnut in to the trunk lid . These parts are only obtainable from Mercedes .They will come with the four brass screws to fix the number plate on to the trunk lid . Not the same as the ones you can buy from the stores ,as they are hexaganal in shape at the base .This is to hold them in the hole that are in the trunk so they dont turn after they are squashed in with the tool .