Volvo 2008 V70 Owner's Manual page 191

To move a hook, fold it down in the direction in which its opening points.
Press the hook down lightly and move it to the desired position.
Fold up the hook. It will lock in place.
NOTE
There should be at least 2 in. (50 cm) between the hooks in the rail.
WARNING
Switch off the engine, apply the parking brake and put the gear selector in P when loading and unloading the vehicle.
206
05 During your trip
Loading
Removing a hook
The load-securing hooks can easily be removed, for example, to clean the rail.
To remove a hook, fold it down in the direction in which its opening points.
Press the hook down lightly and move the it to an opening in the rail.
Pull the hook straight up.
Replace a hook in the rail in the reverse order.