Have you ever gotten a diamond block (or something else) only 1 but wanted more??? Well now you can duplicate it!!! (this only works with stuff that can be placed)
Note 1: If you want to use a different block then in the command below change the words diamond_block to whatever you want to duplicate.
Note 2: You must build a redstone clock leading into the comand block.
Note 3: Once the command is in place the block you want too duplicate next to the command block then start the redstone clock.