The ancient Egyptians believed that they needed a never-ending supply of food for the Afterlife.  When real food was placed in a grave, the correct prayers would continually renew it.  Even an empty food container represented food, and would therefore ensure that the ka of the dead person never went hungry.

Model food, laid out in a pottery offering tray or soul house, was a cheap way of giving food for the dead.  Poorer people used these soul houses, perhaps because they could not afford to give real food.  The food models could include loaves of bread or a whole cow, with beer jars and a pool of water for libations.  Soul houses could be a simple tray of food, or a more detailed model of a house and courtyard.  They were placed at the entrance to the tomb.