GMC 2003 C4C042 Owner's Manual page 238

A. Rubber Pad
B. Hardwood Board
C. Shackle Bracket
D. Lift Chain
4. Remove the remaining slack in the lift chains.
The tow bar swing arm should rest against
the 2" x 12" x 40" hardwood board as shown.
E. Hardwood Beam
F. Bumper
G. Tow Bar
A. Hardwood Board
B. Swing Arm
5. Raise the vehicle to the required height.
5-13