When creating a index or rebuilt, The FILL-FACTOR value determines the percentage of space on each leaf-level page to be filled with data. It is important to set the fill-factor value for each index. In practice a fill-factor value is set to 80 means that 20 percent of each level-level page will be left empty.
USE AdventureWorks2008;
GO
CREATE NONCLUSTERED INDEX IDX_WorkOrder_ProductID
ON Production.WorkOrder(ProductID)
WITH (FILLFACTOR = 80,
PAD_INDEX = ON);
GO