In this mod you may duplicate blocks at will! You will need two things to duplicate blocks: The Duplicator, and the Duplicator stick. first, you need to place the Duplicator floating in the air (if you don't it might have a chance of replacing blocks underneath it). Then, you will need to place the block of your choice (if it is a block with an inventory everything in the inventory won't duplicate with the block being duplicated) on top of the duplicator. Finally, you will need to right click the Duplicator with the Duplicator stick. Then, yay! Your block has been duplicated underneath the duplicator! The best part is about this mod is: whenever you are stuck on a survival world duplicating your blocks just to get tons of modded blocks, you can duplicate those modded blocks also!
EDIT: I just made an item duplicator! The first level will be able to duplicate 10 items max and the second level will be 20 items max. How to use: you place your item(s) in the top left slot and put a duplicator stick in the bottom. Then hit duplicate! I just added levels 3 & 4!