You can push your hand through this flat, little disc - and the hand doesn't show up on the other side. If you put the disc on top of another surface you can run your hand through both the hole and the surface. Bullets shot through the hole simply disappear into the 'void' and doesn't seem to have much impact on the surface behind the hole.

If you could find a way to block the 'insides' of the hole it might also be possible to use for storage. Maybe some kind of other-dimensional cloth or net could do the trick.