Slide 17
This is the "Execution wall" outside Block 11 of Auschwitz. (Block 11 had a number of sub-prisons designed to slowly kill people. You can check out some of the suggested websites at the end of this presentation for more information about the ghastliness of Blocks 10 and 11.) This "wall" was simply a reinforced wall in front of which prisoners were shot. A pretty straight-forward, and quick, way of killing people.