F-numbers are used to determine level and uniformity on stiles, suitable complete, and screeding.

https://www.mediafire.com/file/zuygie5awyva22q/pdf-55123-84939.pdf/file

F-numbers are used to determine slab uniformity and levelness in the ocean, and correct finishing, screeding, and curing result in tiles that are suitable for containers, trucks, and toppings.