GMC Hummer H3 2008 Owner's Handbook Manual page 129

Instrumentation and Controls
To move the cross-rails, do the
following:
1. Turn the key (included with
this system) anti-clockwise to
unlock the cross-rail end cap.
. . . 128
2. Remove both end caps. 3. Pull the lever at each end of
the cross-rail from left to right
to loosen the cross-rail.
4. Move the cross-rail to the
desired position.
- NOTE:
If your vehicle has a sun roof,
there is a cross-rail stop-tab
to prevent the cross-rails
from being moved past the
opening of the sun roof.