Chamberlain 3500D Garage Door Opener User Manual


 
Safety
Reversing Sensor
Horizontal and vertical reinforcement
is needed for lightweight garage doors
(fiberglass, steel, aluminum, door with
glass panels, etc.). See page 20 for details.
Header Wall
Safety
Reversing
Sensor
Support bracket &
fastening hardware
is required. See page 13.
FINISHED CEILING
Extension Spring
OR Torsion Spring