GMC 2006 Sierra - Manual (Page 15)

The seat can also be folded down for more seating
space.
To fold the seat down, do the following:
1. Push the seat cushion while pulling the release
strap which is located under the seat cushion.
Pull the seat cushion down until it latches.
2. After latching the seat cushion, pull up on it to
make sure it is locked.
Rear Seat Operation (Crew Cab)
The second row seat is a 60/40 split seat. Either side of
the rear seat may be flipped and folded for added
cargo space.
Make sure that nothing is under or in front of the seat
and that the head restraints are completely lowered.
To flip and fold the seat, do the following:
1. Pull up on the strap
loop at the rear of the
seat cushion. Then,
pull the seat cushion up
and flip it forward.
2. After folding the seat cushion fully forward, pull the
seatback forward until it is flat. If the seatback
cannot fold flat because it interferes with the
cushion, try moving the front seat forward and/or
bringing the front seat more upright. The lever at the
base of the seat must be turned rearward to
release the seatback.
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