Mercury 1999 Mountaineer Owner's Manual page 168

Driving
To adjust cross-bar position:
1. Slide the locking switches at each
end of the crossbar toward the rear
of the vehicle until UNLOCKED
appears.
2. Slide cross-bar to the desired
location.
3. Lock the cross-bar into position
by pushing the locking switches on
each end of the crossbar toward the
front of the vehicle.
The rear rack can be completely
removed in the UNLOCKED position
by sliding the cross-bar rearward
until it frees the guides.
168