Cadillac 2007 XLR Owner's Manual page 128

7. Move the rear tonneau rearward and up to the
stored position. Pull from the center of the
tonneau to keep pressure even. The rubber
bumper on each corner will fit against
the underside of the trunk decklid.
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8. Push both sides of the rear tonneau
over-center link up until they stop to lock the
linkage.
9. Close the hydraulic pump valve by turning it
clockwise with your hand until it stops.