GMC 1997 Safari Owner's Manual page 120

The pegs inside
the
compartment door are used
to make
sure the button on
the compartment door will
contact the control button
I
on the garage door opener.
Add one peg at a time until the garage door opener
operates with the compartment door closed when you
press the button.
Now, with the compartment
door closed, press the
button again to make sure
the garage door opener
operates properly.
With the garage door opener positioned properly and
the right number of pegs in place, you should only
have to press the button slightly to operate the opener.
Adjust the position of the garage door opener and
add or remove pegs, as needed, until the opener
operates properly. Refer to "Universal Transmitter
(Option)" text in this section.