easy fix for most... if its the license plate which it probaly is, take it off and put a rag or a peice of fome behind it then put it back on... the material will keep it still and it wont rattle any more... if its the trunk lid itself wrap some electrical tape around the stationare hook that the locking mechanism attaches too , usualy black square hook... this will tighten the junction of the trunk and car so the lid will not rattle and its alot cheaper then dynamat