Yeah and to protect the side walls, also if you are away for 6 months there is always the chance that a tyre may go down.
If the car can be started and moved a bit every week then my recomendations are not really necessary.
But if you are like me, storage for 6 months tends to turn into a year at least and it is amazing how stuff deteriorates when left unattended.
Best also to dry the bodywork down well before storing and make sure that the brake discs are well dry.