If you've ever found yourself sitting out in the bush, fighting for survival, against your will. you may have come across instructions that would make life a little more tolerable but those instructions included something you were never able to find. 

The MRE Rock or something can be used as a paper weight, a door stop, a hide a key thing that everyone knows your using to hide a key in, or you know prop up your MRE so you can finally enjoy a warm meal.