Volvo S80 Owner's Manual page 76

NOTE! If your Volvo is equipped with an
integrated booster cushion, you must fold
this out first.
The cover on the rear seat armrest/child seat
has no hinge. The cover must be removed
before the ski hatch is used.
When removing:
Open the cover 30°
pull straight up.
When fitting:
move the cover back in the grooves behind
the upholstery
close the cover