I actually have one of those that is made from two pieces of 1" wood stacked on top of each other. There are slots in the top piece that allows it to move back and forth over the bottom piece held in line by large headed roof nails. When you slide it one way, the holes in the top board line up with the holes in the bottom board and it is deep enough for rifle cases. Slide it back the other way and only the holes in the top board are used and it works for pistol cases.
There are only 50 holes so this is used only during the reloading process and not for storage.