2002 Nissan Sentra alternator belt

While securely holding the hexagonal part in pulley center of drive belt auto-tensioner, move in the direction of arrow (loosening direction of tensioner)
Insert a rod approximately 6 mm (0.24 in) in diameter through the rear of tensioner into retaining boss to lock tensioner pulley.
Leave tensioner pulley arm locked until belt is installed again.
Loosen auxiliary drive belt from water pump pulley in sequence, and remove it.