Chevrolet 2000 Blazer Owner's Manual page 300

The fuel cap is behind a hinged door on driver's side of
your vehicle.
6-6
While refueling, hang the cap by the tether from the
hook on the filler door.
To remove the cap, turn it slowly to the left
(counterclockwise). The cap has a spring in it; if you
let go of the cap too soon, it will spring back
to the right.