Chamberlain C870C Owner's Manual page 22

Invisible Light Beam
Protection Area
Facing the door from inside the garage
Safety Reversing Sensor
6" (15 cm) max. above floor
Carriage Bolt
1/4"-20 x 1/2"
1
2
Carriage Bolt
HARDWARE
Wing Nut
1/4"-20
No more
than 6 inches
(15 cm)
3
Wing Nut