The amount of matter in an object

It's a block for map makers, similar to the command blocks. But this one can [take] a structure that you build in the world, for example a house, and save it. It is then possible to place it in the world multiple times.

So it's basically saving templates and then copying them back into the world at any position. The nice feature is that every structure can be rotated or mirrored when it's placed.

Explanation: