+1 Very good way to cut off grinding by requiring more then one resource.
sabinati wrote:should be metal nugget

While this is surely in jest it might actually be nice to have an improved form of bucket which holds more (not cause its bigger but because the stronger handle allows for heavier loads without breaking), metal tends to make everything better after all, why not water hauling.
How about
2 Blocks of wood + 1 String = "Pail" which holds 5 Liters.
1 Board + 1 nugget hard metal = "Bucket" which holds 10 Liters.
Pail is very simple and dose not even require a saw to make while Bucket is more advanced requiring metal but using it will be twice as fast and thus very much worth the one nugget.