My world, what about the water tank in the toilet?

1, prepare a sufficient number of iron ingots (8 pieces);

2. Take the iron ingot to the tool board;

3. Put the iron ingot into the tool plate according to the following arrangement.

Iron ingot, empty, iron ingot

Iron ingot, empty, iron ingot?

Iron ingot, iron ingot, iron ingot.

If you don't understand, please look at the picture:

4. Synthesis and successful manufacture of water tank.