Savaria Toyota Sienna Owner's Manual page 31

2. Using a generous amount of force, pivot the rear of the bench
downward until the rear latches engage with the hooks in the floor.
If one or both latches fail to engage, pull the black release lever at
the side of the bench and pivot it downward once again with more
force. If difficulties arise, contact Savaria® Vehicle Group.
3. Flip the backrests and headrests up.
Removal:
It takes a minimum of two people to install/remove this bench seat.
1. Lower the backrests and headrests.
2. Locate the black thumb screw handles and twist them in the
counter-clockwise direction until both are completely removed.
Put them in a safe place, such as the storage bin at the rear of the
van or the spare tire cover pocket.
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