Craftsman 1/2 HP GARAGE DOOR OPENER 139.53978SRT - Manual (Page 16)

Installation Step 4
Position the Opener
Follow instructions which apply to your door
type as illustrated.
To prevent damage to steel, aluminum,
fiberglass or glass panel doors, do not rest the
opener on the door without using a 2x4.
A 2x4 laid flat is convenient for setting an ideal
door-to-T-rail distance.
• Raise the opener onto a stepladder as shown. You
will need help at this point if the ladder is not tall
enough.
• Open the door all the way and place a 2x4 laid flat
on the top section beneath the rail.
If the top panel hits the trolley when you raise
the door, pull down on the trolley release arm to
disconnect die inner and outer sections. The
trolley can remain disconnected until Step 12 is
completed.
Trolley
’ With the door fully open and parallel to the floor,
measure the distance from the floor to the top of
the door.
’ Using a stepladder as a support, raise the opener
to this height (it will be at a slight angle as shown).
• The top of the door should be level with the top of
the opener. Do not position the opener more than
2" above this point.
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