Toyota 2011 Matrix Owner's Manual page 46

Seat belts
If belt is fully extended, then retracted even slightly, it cannot be
re-extended beyond that point, unless fully retracted again. This feature
is used to help hold child restraint systems securely.
To find more information about seat belts, and how to install a child
restraint system, refer to the Owner's Manual.
Spare tire & tools
Tool location
Removing the spare tire
(1)
(1) Turn the knobs to the "UNLOCK" position and remove the deck boards.
(2) Loosen the center fastener that secures the spare tire.
Refer to the Owner's Manual for tire changing and jack positioning
procedures.
Keep as low on
hips as possible
Spare tire
Jack
21
Too high
Wheel nut wrench
(2)
Take up slack
Jack handle