Three thieves are in a house...

Three thieves are in a house when suddenly they hear someone come through the door. In a hurry to hide as soon as possible, each finds a gunny sack to hide inside. When the owner comes in and finds three unfamiliar sacks, he kicks the first one, the thief inside thinks quick and makes a sound similar to grains being moved. The owner moves to the second and kicks it, this one makes the sound of walnuts being banged together. The owner, almost relaxed now, kicks the third sack, which doesn't make any sound. A bit surprised he kicks it again and again and again harder each time, till finally the angry thieve inside yells out: "It's flour you stupid piece of s**t, it doesn't make a sound".