The primary role of the parcel shelf is to put things on. It also keeps any belongings in the boot out of sight reducing the risk of theft. Furthermore, it can act as a barrier to minimise noise from the rear of the vehicle.
Many vehicles on the road today do not have a parcel shelf fitted. Sometimes the parcel shelf mountings snap, become worn/dirty or are removed to increase the storage capacity which as a result are either lost or the vehicle is sold on without one.
If your parcel shelf is damaged and needs replacing or your vehicle never had one , it can be easily replaced at low cost and fitted with minimal effort.