sp_chgattribute allows you to store a fillfactor percentage for each index and for the table. The fillfactor you set with sp_chgattribute is applied when you:
Run reorg rebuild to restore the cluster ratios of data-only-locked tables and indexes.
Use alter table...lock to change the locking scheme for a table or you use an alter table...add/modify command that requires copying the table.
Run create clustered index and there is a value stored for the table.
The stored fillfactor is not applied when nonclustered indexes are rebuilt as a result of a create clustered index command:
If a fillfactor value is specified with create clustered index, that value is applied to each nonclustered index.
If no fillfactor value is specified with create clustered index, the server-wide default value (set with the default fill factor percent configuration parameter) is applied to all indexes.
