What is USING keyword in SQL Server 2008?

Question

I know the beautiful usage of the SQL clause "USING": it is similar to NATURAL JOIN but you must detail the join columns; you can join more simply (and faster) the tables that have the same key and foreign key, and the output of queries doesn't contain redundant fields.

However SQL Server 2008 doesn't support the JOIN with the USING keyword, but, as you can see in the link, it uses this keyword. Why?

Supervisory

USING is part of MERGE. Don't assume that an entry in the list of reserved keywords means that it functions the same as it does in some other platform... – Checkmate

yes it is! you are right – Supervisory