This one of my absolute favorites.
Large storage capacity and a stirdy construction.
 
This is how I found it. Aparently there are many lives after the postal service.
I cut away every other thread in the bottom part to make larger holes. The small ones are 3x6,5cm and the large ones 6,5x6,5cm (that is just a little smaller than 2 inches).
 
  A piece of aluminum sheet metal leaning at the bottom and it is ready.
 
  This little Shetland pony is eating through the small holes even though no one using the large ones.