Chevrolet 2004 Silverado 1500 Pickup Owner's Manual page 158

A. Back rail
B. Side rail
C. Rear bow
2. Remove the tonneau cover from the notch in the
front rail on the driver's side of the vehicle.
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D. Center bow
E. Front bow
F. Front rail
3. Remove the three bows by gently pushing them
against the spring-loaded end. The three bows
are labeled front, center, rear to remind you of the
order in which to reinstall them.