mlozzi, the vertical rod adjusts the position of the tensioner while the horozintal center bolt "locks" it in place. Turning the vertical adjuster rod before loosening the center bolt will destroy the tensioner. In fact, don't be surprised if after installing the new belt the tensioner will not retighten. In that case you need to buy a new tensioner, and installation is quite involved due to the power steering pump limiting access.

As I recall removing the power steering pump pulley may provide enough clearance to remove/reinstall the tensioner. If you decide on that approach loosen the power steering pump pulley bolts before removing the belt because the belt will keep the pulley from turning.

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Fred Hoelzle