This inventory of March 31, 1943 was written up at the time Krematorium II was formally completed for the Auschwitz-Birkenau camp. (It had actually been tested for the first time in early March.)
At the top left, we see the building being inventoried, "Krematorium 2," also known as "KGL 30." This building is one of the large killing/cremation facilities built at Auschwitz-Birkenau.
Below that, the first two rooms listed ("Raum 1," "Raum 2") have been written in as "Leichenkeller," which means "morgue." The Leichenkeller numbered "one" is the homicidal gassing chamber.
Near the top right, we see that there are two inventory items which have been written in by hand. They are a little difficult to make out, especially in this reproduction, but they read "Drahtnetzeinschiebvorrichtung" and "Holzblenden." The numeral 4 is written in each category. In this closeup, the text has been rotated ninety degrees:
"Drahtnetzeinschiebvorrichtung" is a large compound word. Words like this are quite common in the German language. Its meaning is put together from the words which form it:
der Draht - wire
das Netz - grid, net
einschieben - insert
die Vorrichtung - device, mechanism
This is best translated as "wire-mesh insertion device" or "wire-mesh introduction device."
"Holzblenden" means "wooden covers."
Why is this significant? The room labeled as a morgue, the Leichenkeller, was actually the homicidal gassing chamber in this Krematorium building. We know from numerous sources - aerial photographs, examination of the ruins of the building as they stand today, and the testimony both of the Jewish witnesses and of the perpetrators - that there were holes in the roof, four in number, where the poison Zyklon-B was inserted.
This wartime document confirms key aspects of the testimonies. The Zyklon granules were poured into the holes, falling into the wire columns which held them and allowed them to give off their poison gas freely. The wooden covers were placed over those holes to keep the gas contained (though the SS men on the roof surely wore gas masks for safety) and to shut out the screams of those below.
The wire mesh existed primarily to make cleanup faster and safer. If the small pellets had simply fallen onto the floor, they might continue to give off dangerous gas even after everyone had died. But since they were poured into a wire "core" which could be lifted out of the gas chamber and onto the roof after the killing operation was complete, they would pose no danger to anyone inside. Removal of corpses could begin much sooner, thus making the entire killing process more efficient.
This document is reproduced in Pressac, Jean Claude, Auschwitz: Technique and Operation of the Gas Chambers, The Beate Klarsfeld Foundation, New York, 1989, p. 430. Its source is given as Auschwitz State Museum Archive reference BW 30/43, p. 12.
As Pressac points out (pp. 429-30), it is Leichenkeller 1 which contains the wire-mesh introduction devices and the wooden covers, though the numerals "4" for these items are entered on the second line. We know the numbers are switched because all the other evidence converges on Leichenkeller 1 as the gas chamber, and not Leichenkeller 2 (which was the room where the victims undressed). Pressac also points out that there are other figures which are switched between the two lines, referencing this document against drawing 2197 from the October Revolution archives.