Chamberlain B353 Owner's Manual page 7

Assembly
STEP 2 Fasten the Rail to the Motor Unit
To avoid SERIOUS damage to garage door opener, use ONLY those bolts/fasteners mounted in the top of the
opener.
1. Insert a 1/4"-20 x 1-3/4" bolt into the cover protection bolt hole on the back end of the rail as shown. Tighten
securely with a 1/4"-20 lock nut. DO NOT overtighten.
2. Remove the bolts from the top of the motor unit.
3. Use the carton to support the front end of the rail.
4. Place the "U" bracket, flat side down onto the motor unit and align the bracket holes with the bolt holes.
5. Fasten the "U" bracket with the previously removed bolts; DO NOT use any power tools. The use of power
tools may permanently damage the garage door opener.
Bolts (Mounted in the
garage door opener)
"U" Bracket
Bolt
Cover Protection
Bolt Hole
Lock Nut
7
HARDWARE
Bolt
1/4"-20x1-3/4"
Lock Nut
1/4"-20