Currently compiled against Minecraft Version 1.12.1 and prevents the carpet/rail dupe glitch that is built into vanilla using slime blocks.



Basically build this machine, the carpet on the end (or any rail) placed where the carpet is, will break and replace itself dropping a copy of the item every time the observer on the right updates. If you create a clock here to update it quickly then you can mass dupe carpets / rails very fast. Not a HUGE ordeal but if players can sell carpets or rails in your shop then it has the potential to destroy your economy quite quickly.